Form II Science - Chemical Reactions I Booklet 2024 PDF
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Sydney Grammar School
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Summary
This is a Form II Science booklet covering Topic 4: Chemical Reactions I for Sydney Grammar School. It contains a detailed table of contents with various topics like naming, balancing, and types of chemical reactions.
Full Transcript
#### **FORM II** #### **Science** #### **Topic 4: Chemical Reactions I** #### **Name:** #### #### **Master:** #### {#section-2.BodyText} {#section-3.BodyText} {#section-4.BodyText} {#section-5.BodyText} {#section-6.BodyText} {#section-7.BodyText} {#section-8.BodyText} {#secti...
#### **FORM II** #### **Science** #### **Topic 4: Chemical Reactions I** #### **Name:** #### #### **Master:** #### {#section-2.BodyText} {#section-3.BodyText} {#section-4.BodyText} {#section-5.BodyText} {#section-6.BodyText} {#section-7.BodyText} {#section-8.BodyText} {#section-9.BodyText} {#section-10.BodyText} {#section-11.BodyText} **Contents** {#contents.TOCHeading} ============ [**Revision of Elements and Compounds** 4](#revision-of-elements-and-compounds) [**Elements** 4](#elements) [**Metals** 4](#metals) [**Non-Metals** 4](#non-metals) [**The Periodic Table** 4](#the-periodic-table) [**Naming Compounds** 7](#naming-compounds) [**Activity 1: Formulae of non-metals bonded to non-metals** 9](#activity-1-formulae-of-non-metals-bonded-to-non-metals) [**Activity 2: Formulae of metals bonded to non-metals** 10](#activity-2-formulae-of-metals-bonded-to-non-metals) [**Chemical Formulae in review** 11](#chemical-formulae-in-review) [**Activity 3: Formulae Practice** 12](#activity-3-formulae-practice) [Signs of a Chemical Reaction 13](#signs-of-a-chemical-reaction) [Definition of Reactants and Products and Word Equations 14](#definition-of-reactants-and-products-and-word-equations) [Balanced Chemical Equations 15](#balanced-chemical-equations) [States 16](#states) [**Writing Chemical Equations** 17](#writing-chemical-equations) [**Activity 4: Pre-Balancing Practice** 20](#activity-4-pre-balancing-practice) [**Activity 5: Balancing Practice** 23](#activity-5-balancing-practice) [**Activity 6: Harder Balancing Practice** 24](#activity-6-harder-balancing-practice) [**Activity 7: Writing Equations** 25](#activity-7-writing-equations) [Reaction Types 27](#reaction-types) [**Activity 8: Reaction Types** 29](#activity-8-reaction-types) [**Activity 9: Harder Balanced Equations** 33](#activity-9-harder-balanced-equations) [**Investigation:** **Mass Changes for Physical and Chemical** 34](#investigation-mass-changes-for-physical-and-chemical) [**Investigation:** **Law of Conservation of Mass** 36](#investigation-law-of-conservation-of-mass) [**Investigation:** **Factors that affect the corrosion of iron** 37](#investigation-factors-that-affect-the-corrosion-of-iron) [**Practice Questions** 39](#practice-questions) [Summary of Chemical Reactions I 47](#summary-of-chemical-reactions-i) **Outcomes:** +-----------------------------------+-----------------------------------+ | **OUTCOMES At the end of this | | | topic, pupils should be able | | | to:** | | +===================================+===================================+ | 1. 1 | **DESCRIBE** the characteristics | | | of a chemical change whereby a | | | new substance is formed. This may | | | be identified by: | | | | | | - - - - - | +-----------------------------------+-----------------------------------+ | 2. 3 | **UNDERSTAND** and **WRITE** word | | | equations for the following | | | reactions: | | | | | | - - - - | +-----------------------------------+-----------------------------------+ | 3. 4 | **DEFINE** the terms 'reactants' | | | and 'products'. **IDENTIFY** | | | reactants and products in a | | | chemical reaction. | +-----------------------------------+-----------------------------------+ | 4. 5 | **RECALL** the Law of | | | Conservation of Mass which states | | | that, in chemical reactions, the | | | total mass remains unchanged. | | | Thus for a reaction that goes to | | | completion, the total mass of | | | products equals the total mass of | | | reactants. | +-----------------------------------+-----------------------------------+ | 5. 6 | **APPRECIATE** that since matter | | | is neither created nor destroyed | | | in chemical reactions, the number | | | of atoms of each element must be | | | 'balanced' (the same number of | | | each atom in the reactants and in | | | the products). | +-----------------------------------+-----------------------------------+ | 6. 7 | **RECALL** the formulas of some | | | common binary compounds from | | | Topic 2 using valency. **NAME** | | | some simple compounds: | | | | | | - - | +-----------------------------------+-----------------------------------+ | 7. 8 | **BALANCE** simple chemical | | | equations | +-----------------------------------+-----------------------------------+ | 8. 9 | **INCLUDE** states in balanced | | | chemical equations. | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | **PRACTICAL SKILLS: During this | | | topic this topic, you will:** | | +===================================+===================================+ | 9. | **DESIGN** an experiment to | | | investigate factors affecting the | | | corrosion of iron. | +-----------------------------------+-----------------------------------+ | 10. | **VERIFY** the conservation of | | | mass in chemical reactions. | +-----------------------------------+-----------------------------------+ | 11. | **USE** the conservation of mass | | | to calculate the mass of products | | | or reactants in chemical | | | reactions. | +-----------------------------------+-----------------------------------+ **\ ** **Revision of Elements and Compounds** ====================================== ### **Elements** An **element** is a single substance that is made up of only one kind of atom and which cannot be split into anything simpler by any chemical process. For example, magnesium is an element and is made up of magnesium atoms only. No matter what chemical reaction you do with it, it is not possible to obtain a simpler substance than magnesium from it. As many as 105 elements have been identified. Of these, 15 do not occur in nature and are man-made, e.g. plutonium. However, a vast majority of elements occur naturally, usually in combination with other elements. Most of the elements are solid and **metallic**, e.g. copper and lead, whilst some are solid and **non-metallic**, e.g. sulfur and carbon. Some, for example, mercury (a metal) and bromine (a non-metal) are liquid, whilst other non-metals such as hydrogen and nitrogen are gases at standard temperature and pressure. ### **Metals** About 70 of the elements are **metals**. Although they all look different, they have many properties in common. 1\. They are good conductors of electricity and heat. 2\. Except for mercury, they are all solids at room temperature and most of them have high melting points. 3\. Most of them can be hammered into different shapes (they are **malleable**). 4\. Most of them can be drawn into wires (they are **ductile**). ### **Non-Metals** About 20 of the elements are **non-metals**. They are quite different from metals. 1\. They are poor conductors of heat and electricity (carbon is an exception). 2\. They usually have low melting points (11 of them are gases and 1 is a liquid at room temperature). 3\. When solid non-metals are hammered, they break up, i.e. they are **brittle**. ### **The Periodic Table** The Russian scientist Dmitri Mendeleev (1834-1907) arranged the known elements into a table called the Periodic Table. He used the physical and chemical properties of the elements to sort them into groups. He even left spaces for elements he believed were missing. Those elements have since been found. A modern Periodic Table is shown on the next page. The areas on the left of the bold zig-zag line contain metallic elements and the area to the right of the bold zig-zag line contains the non-metals. #### The Structure of the Periodic Table The table has eight groups of elements, plus a block of **transition metals**. The groups are numbered above the columns. Some of the groups have special names: Elements in the same group have similar chemical properties and have the same number of electrons in their outer shell. The horizontal rows in the table are called **periods**. The block in the centre, the **transition metals~,~** contain many common metals. These elements can form ions of varying combining powers, produce coloured compounds and many of them have high melting points **Compounds** A compound contains atoms of different elements joined together. Compounds are formed from chemical reactions where: - elements react with other elements, for example, magnesium burning in oxygen. - elements react with compounds, for example, iron and copper(II) chloride. - compounds react with other compounds, for example, silver nitrate and sodium chloride. The properties of a compound are generally not the same as the properties of the compounds or elements from which it was made. The formula of a compound shows the number and types of atoms present in a formula unit. There is a difference between the terms compounds and molecules as can be shown in the diagram below. ##### ### **Naming Compounds** +-----------------------------------------------------------------------+ | **RECALL** the formulas of some common binary compounds from Topic 2 | | using valency. **NAME** some simple compounds: | | | | - - | +-----------------------------------------------------------------------+ The way in which compounds are named depends on the type of elements they contain. There are four combinations of elements that must be considered when naming compounds. These are combinations that contain: 1. Non-metal elements only. 2. Metal and non-metal elements 3. Transition metals and non-metals -- learnt next year 4. Polyatomic ions -- learnt next year #### Non-metal elements only. In this case the first elements name is not changed and the second has its final syllable replaced with 'ide'. Generally, these compounds have names which tell you the formula, for example: ------------------------ --------- Name of Compound Formula carbon monoxide CO sulfur dioxide SO~2~ carbon dioxide CO~2~ sulfur trioxide SO~3~ carbon tetrachloride CCl~4~ phosphorus trichloride PCl~3~ carbon disulfide CS~2~ ------------------------ --------- ------- ----- ------ -------- -------- ------- -------- ------- ------- ------- mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- 1 2 3 4 5 6 7 8 9 10 ------- ----- ------ -------- -------- ------- -------- ------- ------- ------- #### Metal and non-metal elements #### The names of these compounds (also called ionic compounds) always start with the name of the metal. It is followed by the name of the non-metal with the last syllable removed and the suffix '-ide' added. For example, the compound formed when the metal sodium reacts with chlor**ine** gas is called sodium chlor**ide**. The key to working out formulas for these compounds is their position in the Periodic Table. The group number indicates the valency or combining power of the elements. Groups I - IV the combining power is the same as the group number. Groups V - VII the combining power is equal to eight minus the group number, e.g. group VII elements have a combining power of one. Learning a few formulas by heart will prove to be very beneficial. **Example 1:** A Group I element, sodium, combining with a Group VII element, chlorine Compound Name: sodium chloride Formula: NaCl~(s)~ This ratio of combination, 1 : 1, will be the same for any Group I metal combining with any Group VII non-metal. We would therefore expect the formula of potassium bromide to be KBr~(s)~, and so it is! Note that this is consistent with our earlier consideration of the net charge. **Example 2:** A Group II element, magnesium, with a Group VII element, chlorine Compound Name: magnesium chloride Formula: MgCl~2(s)~ ### **Activity 1: Formulae of non-metals bonded to non-metals** The name of a compound formed when a non-metal bonds to non-metal (also called molecular compounds) contains prefixes, which indicate how many parts of each element are present. Complete the following table that contains some other oxides of nitrogen. ----------------------- ------------- **Name** **Formula** dinitrogen monoxide N~2~O~(g)~ NO~(g)~ N~2~O~3(g)~ NO~2(g)~ dinitrogen pentaoxide dinitrogen tetraoxide ----------------------- ------------- Now try these. -------------------------- ------------- **Name** **Formula** carbon tetrachloride BF~3(g)~ SF~6(g)~ phosphorus pentachloride diphosphorus pentaoxide -------------------------- ------------- ### ** Activity 2: Formulae of metals bonded to non-metals** 1\. (a) Write the chemical formulas of the following compounds: 2\. Formulas of some ionic compounds can be worked out easily because they follow the **same pattern** as other elements with the **same position in the Periodic Table**. ------------------- ------------- ------------------------ **Compound** **Formula** **By comparison with** calcium sulfide MgO~(s)~ beryllium bromide MgCl~2(s)~ potassium iodide NaCl~(s)~ lithium sulfide Na~2~O~(s)~ aluminium sulfide Al~2~O~3(s)~ \\ ------------------- ------------- ------------------------ Hydrogen reacts with non-metal elements forming a special set of molecular compounds. Using the position of the non-metal as a guide, we can appreciate that carbon is equivalent to four hydrogen's, nitrogen three, oxygen two and fluorine one. Hence the following molecular formulas: CH~4(g)~ = methane \* NH~3(g)~ = ammonia \* H~2~O~(l)~ = water \* HF~(g)~ = hydrogen fluoride \* indicates a special name which must be remembered. These formulas can serve as 'a guide' for the formulas of compounds formed by other elements with similar positions in the Periodic Table. ### ### **Chemical Formulae in review** Do you ? a. The **chemical formula of elements** may be: b. Simple **binary compounds** may be: ------------ -- NH~3(g)~ CH~4(g)~ H~2~O~(l)~ ------------ -- ### **Activity 3: Formulae Practice** **IUPAC name** **Formula** -------------------------------- -------------- magnesium nitride (solid) sulfur dioxide (gas) potassium fluoride (solid) magnesium chloride (solid) dioxygen difluoride (liquid) lithium oxide (solid) phosphorus pentafluoride (gas) nitrogen triiodide (solid) methane (gas) aluminium sulfide (solid) nitrogen monoxide (gas) CaO~(s)~ Cl~2~O~3(s)~ K~2~S~(s)~ NH~3(g)~ BeF~2(s)~ O~2(g)~ CO~2(g)~ Al~2~O~3(s)~ P~4~O~6(s)~ Ca~3~N~2(s)~ H~2~O~(l)~ Signs of a Chemical Reaction ---------------------------- +-----------------------------------------------------------------------+ | **DESCRIBE** the characteristics of a chemical change whereby a new | | substance is formed. This may be identified by: | | | | - - - - | | | | disappearance of reactants. | +-----------------------------------------------------------------------+ A chemical reaction has taken place when a new substance is formed (a new substance is formed by the rearrangement of atoms) A chemical reaction may be identified from a number of observations: - colour change - precipitate forms (solid forms when two solutions mixed) - gas is given off (Mg in acid - H~2~ bubbles) - production of heat (Mg in acid - test tube gets warm) - disappearance of the reactants Watch ClickView video: Chemical Change Complete Schoology Quiz: Signs of a Chemical Reaction  Unit 4.1 Definition of Reactants and Products and Word Equations ------------------------------------------------------- -------------------------------------------------------------------------------------------------------------- **DEFINE** the terms 'reactants' and 'products'. **IDENTIFY** reactants and products in a chemical reaction. -------------------------------------------------------------------------------------------------------------- **Reactan**t is a substance that takes part in a chemical reaction. It is present before the chemical reaction takes place. The more general term, reagent, is sometimes used to list all the substances present at the start of the reaction. **Product** is a substance formed in a chemical reaction. **Word equations** are written to show simply what is happening. Reactants are written on the left-hand side and products are written on the right. If there is more than one reactant / product, then the '+' sign is used to join them. An arrow is used to separate reactants from products. This arrow between them can be read as "turns into". Anything over the arrow is required for the reaction but is not consumed in the reaction. Note that the '=' sign is not used. Word equations can be written for both chemical and physical changes. For example: Write the word equation for hydrogen gas reacting with oxygen gas to form water during the pop test. **\ ** Balanced Chemical Equations --------------------------- **RECALL** the Law of Conservation of Mass which states that, in chemical reactions, the total mass remains unchanged. Thus for a reaction that goes to completion, the total mass of products equals the total mass of reactants. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ **APPRECIATE** that since matter is neither created nor destroyed in chemical reactions, the number of atoms of each element must be 'balanced' (the same number of each atom in the reactants and in the products). While word equations are a useful way of representing chemical reactions, a better method of summarising information about chemical changes involves the replacement of words with chemical formulas. When chemical formulas are used in this way, care is taken to ensure that all atoms present before the chemical change are also present after the change. This is essential because mass is **not** destroyed in a chemical change, i.e. the Law of Conservation of Mass must be upheld. This law can be stated as follows: **"In a chemical change, the total mass of the reactants is equal to the total mass of the products".** A statement involving chemical formulas to represent reactants and products in appropriate amounts is known as a **chemical** **equation**. The figure below is an example of a chemical reaction that illustrates the law of conservation of mass. The law of conservation of mass When the grey magnesium is ignited, it burns brightly, combining with oxygen from the air to form a white powder, magnesium oxide. If 0.024 g of magnesium is burned and this reacts with 0.016 g of oxygen, 0.040 g of magnesium oxide would be produced. The sum of the masses of the magnesium and the oxygen that react equals the mass of the magnesium oxide produced. Thus, mass is conserved. As matter is neither created nor destroyed in chemical reactions, the number of atoms of each type in the reactants MUST be the same number as in the products -- thus atoms of each element must be '**balanced**' in a chemical equation. Chemical equations using either words or chemical symbols describe a reaction between *substances*. Remember that some substances occur in nature as "groups of individual atoms" and some occur as "groups of molecules". For example, metals versus gases (such as nitrogen, oxygen, hydrogen, chlorine etc). In order to be able to write word equations and chemical equations for the reactions, you perform you will need to: 1\. know the *state* of the elements and compounds. 2\. be able to name the compounds (both molecular and ionic). 3\. be able to write the chemical formulas of the compounds. This requires that you: ### States Chemical reactions occur between substances in all three of the states in which matter can exist. For example, solids can react with solids, liquids or gases, and so on. Substances in solution can also be involved in chemical reactions. Water is commonly the solvent, and it is usually the solute that reacts. In these reactions, the state of the substances is 'aqueous'. In describing a chemical reaction, it is important to include the states of each substance. The states are abbreviated in chemical equations by including the following letters as subscripts. **solid - (s) liquid - (l) gas - (g) aqueous - (aq)** e.g. a lump of sodium is Na~(s)~; a flask of mercury is Hg~(l)~ or bromine, Br~2(l)~; a jar of oxygen gas is O~2(g)~; a solution of sodium chloride is NaCl~(aq)~. The state of a substance will depend on the conditions under which the reaction is taking place. Some helpful points to remember if a reaction occurs under standard conditions, i.e. room temperature and normal atmospheric pressure, are that: - metallic substances will be solid (except mercury). - non-metallic substances may be solid (sulfur), liquid (bromine) or gas (oxygen) - check the Periodic Table. - salts (metal/non-metal compounds) will be solid **or** aqueous if dissolved in water. ### **Writing Chemical Equations** **BALANCE** simple chemical equations ---------------------------------------------------- **INCLUDE** states in balanced chemical equations. Listed below are the steps involved in writing a correct chemical equation. Remember that equations show how **substances** react. **Step 1.** Write down the "word equation" showing the identities of the reactants and products involved in the reaction. While it is not essential to write down the word equation, it is necessary that one knows the names of all the reactants and products and it is a helpful practice when first learning to write chemical equations. When you have become competent in writing chemical equations, the need to write word equations will no longer exist. **Step 2.** Under each name in the word equation, write the correct chemical formula for each substance. Indicate the "state" of the substance by using an abbreviation of the following kind: **Step 3.** Check that all of the atoms present on the reactant side of the equation are also present on the products side of the equation. Remember the equation must obey the Law of Conservation of Mass. If there is an imbalance in the number of atoms of one or more elements, the equation must be "balanced". **Step 4.** When "balancing an equation", coefficients (whole numbers) are placed in front of the formulas in order to change the amount of substance involved. Remember, balancing does not involve changing the formulas, only the amount of substance present. Consider the pop test where hydrogen reacts with oxygen to make water. **Step 1.** hydrogen + oxygen → water **Step 2.** H~2(s)~ + O~2(g)~ → H~2~O~(l)~ **Step 3.** **Check!** An imbalance does exist in the number of atoms. In this case, we have too few oxygen atoms on the product side. We must address this imbalance. **Step 4.** Using '2' as a coefficient, we balance the equation by first placing '2' in front of the formula for water and then, realising the hydrogen atoms were unbalanced, a '2' in front of the formula for hydrogen. The correct equation is therefore: 2 H~2(s)~ + O~2(g)~ → 2 H~2~O~(l)~ To illustrate these steps, we will take the reaction between sodium metal and chlorine gas to produce solid sodium chloride. See below. **Step 1.** sodium + chlorine → sodium chloride **Step 2.** Na~(s)~ + Cl~2(g)~ → NaCl~(s)~ **Step 3.** **Check!** An imbalance does exist in the number of atoms. In this case, we have an insufficient number of chlorine atoms on the product side. We must address this imbalance. **Step 4.** Using '2' as a coefficient, we balance the equation by first placing '2' in front of the formula for sodium chloride and then, realising the sodium atoms were unbalanced, a '2' in front of the formula for metallic sodium. The correct equation is therefore: 2Na~(s)~ + Cl~2(g)~ → 2NaCl~(s)~ ### **Activity 4: Pre-Balancing Practice** 1. A list of compounds and their formulae are shown in the following table. **Chemical Name** **Formula** --------------------- ------------- gallium oxide Ga~2~O~3~ magnesium carbonate MgCO~3~ magnesium sulfate MgSO~4~ potassium carbonate K~2~CO~3~ **gallium oxide** **magnesium carbonate** **magnesium sulfate** **potassium carbonate** ----- ------------------- ------------------------- ----------------------- ------------------------- (A) Y Z X W (B) Y X W Z (C) Z Y X W (D) X W Z Y 2. The diagram below represents a chemical change involving nitrogen and hydrogen. Which equation represents this chemical change? A. B. C. D. ~\ ~ 3. Silver tarnishes when it reacts with sulfur from the air. This tarnishing process creates a black layer of silver sulfide that can be cleaned off by dipping the silver object into a basic solution containing aluminium foil. In this metal displacement reaction, the aluminium displaces the silver from the silver sulfide to form aluminium sulfide, leaving the silver metal free. Which option represents this chemical reaction? 4. The diagram below represents a chemical change involving oxygen and hydrogen. Which equation represents this chemical change? A. B. C. D. Use the following diagram to answer questions 5-7. 5. In which step would new substances be formed? a. Step I b. Step II c. Step III d. Step IV 6. When evaporation is complete after step IV, what substance would remain in the dish? e. Acid f. Metal g. Salt h. Water 7. Which piece of equipment would be most suitable to use instead of a beaker in steep II? a\.  ------------------------------------------------------------ --------------------------------------------------------------------- b\.  ### **\ ** ### **Activity 5: Balancing Practice** Balance the following by writing coefficients in front of the formulae. 1. Ca + O~2~ → CaO 2. Na + S → Na~2~S 3. Al + O~2~ → Al~2~O~3~ 4. P + O~2~ → P~4~O~10~ 5. C + Br~2~ → CBr~4~ 6. P + F~2~ → PF~3~ 7. Sr + N~2~ → Sr~3~N~2~ 8. N~2~ + O~2~ → N~2~O 9. S + F~2~ → SF~6~ 10. Be + O~2~ → BeO 11. P + Cl~2~ → PCl~5~ 12. Si + H~2~ → SiH~4~ 13. N~2~ + O~2~ → N~2~O~5~ 14. N~2~ + H~2~ → NH~3~ ### **Activity 6: Harder Balancing Practice** Balance these equations by writing coefficients in front of the formulae. *Note everything in brackets is multiplied by its following number,* *e.g. (CN)~2~ means 2 x C AND 2 x N.* 1\) \_\_\_\_ AlBr~3~ + \_\_\_\_ K \_\_\_\_ KBr + \_\_\_\_ Al 2\) \_\_\_\_ FeO + \_\_\_\_ PdF~2~ \_\_\_\_ FeF~2~ + \_\_\_\_ PdO 3\) \_\_\_\_ P~4~ + \_\_\_\_ Br~2~ \_\_\_\_ PBr~3~ 4\) \_\_\_\_ LiCl + \_\_\_\_ Br~2~ \_\_\_\_ LiBr + \_\_\_\_ Cl~2~ 5\) \_\_\_\_ PbBr~2~ + \_\_\_\_ HCl \_\_\_\_ HBr + \_\_\_\_ PbCl~2~ 6\) \_\_\_\_ CoBr~3~ + \_\_\_\_ CaSO~4~ \_\_\_\_ CaBr~2~ + \_\_\_\_ Co~2~(SO~4~)~3~ 7\) \_\_\_\_ Na~3~P + \_\_\_\_ CaF~2~ \_\_\_\_ NaF + \_\_\_\_ Ca~3~P~2~ 8\) \_\_\_\_ Mn + \_\_\_\_ HI \_\_\_\_ H~2~ + \_\_\_\_ MnI~3~ 9\) \_\_\_\_ Li~3~PO~4~ + \_\_\_\_ NaBr \_\_\_\_ Na~3~PO~4~ + \_\_\_\_ LiBr 10\) \_\_\_\_ CaF~2~ + \_\_\_\_ Li~2~SO~4~ \_\_\_\_ CaSO~4~ + \_\_\_\_ LiF 11\) \_\_\_\_ HBr + \_\_\_\_ Mg(OH)~2~ \_\_\_\_ MgBr~2~ + \_\_\_\_ H~2~O 12\) \_\_\_\_ LiNO~3~ + \_\_\_\_ CaBr~2~ \_\_\_\_ Ca(NO~3~)~2~ + \_\_\_\_ LiBr 13\) \_\_\_\_ AgNO~3~ + \_\_\_\_ Li \_\_\_\_ LiNO~3~ + \_\_\_\_ Ag 14\) \_\_\_\_ Si(OH)~4~ + \_\_\_\_ NaBr \_\_\_\_ SiBr~4~ + \_\_\_\_ NaOH 15\) \_\_\_\_ NaCN + \_\_\_\_ CuCO~3~ \_\_\_\_ Na~2~CO~3~ + \_\_\_\_ Cu(CN)~2~ ### **Activity 7: Writing Equations** 1\. Practise your skill in "balancing" equations by completing the following: 2\. Use the following word equations to write complete chemical equations. Remember that some substances exist as molecules. **Note**: If you are unsure of the states of any of these substances, check with your Science Master and remember that most metals + non-metals are solids. 3\. Write word equations and balanced chemical equations for each of the following reactions. a. b. c. d. If a small amount of melted sodium is lowered into a jar of chlorine gas, it burns with an intense yellow flame to form a white powder, sodium chloride. e. When a wad of steel wool (iron) is ignited in air and then quickly plunged into a jar of chlorine, it continues to burn, forming dense red-brown fumes of iron(III) chloride that condenses as solid particles on the wall of the gas jar. (Note the (III) means that iron has a valency of 3 in this compound). f. When aluminium turnings are heated with yellow sulfur, a white powder, aluminium sulfide is formed. g. At the high temperature of the combustion chamber of a motor car, nitrogen and oxygen from the air combine to form nitric oxide (nitrogen monoxide). h. If a mixture of nitrogen and hydrogen gases is passed over a white hot platinum filament, some ammonia gas is formed. i. When silver is heated with yellow sulfur, black silver sulfide is formed. (Hint: silver compounds always have a valency of 1 for silver). j. If small pieces of aluminium foil are dropped into liquid bromine, thick yellow fumes are formed; these condense to solid aluminium bromide. Reaction Types -------------- +-----------------------------------------------------------------------+ | **UNDERSTAND** and **WRITE** word equations for the following | | reactions: | | | | - - - | | | | combustion | +-----------------------------------------------------------------------+ 1. [Direct Synthesis] -- making a substance from simpler substances, usually from its component elements e.g. iron + sulfur makes 'fool's gold' iron sulfide 2. [Decomposition] -- breaking down of a compound into smaller compounds. Usually done with heat or electrolysis e.g. decomposing a carbonate into CO~2~ with heat. Can be recognised when there are more products than reactants. 3. [Combustion] -- reaction with oxygen gas from air in a fast reaction e.g. burning coal or magnesium. Note that combustion is differentiated from corrosion in that it gives out large amounts of heat. When a question says 'burns in air', this always means 'reacts with oxygen'. **Complete** combustion of carbon-based substances produces carbon dioxide and water. Important for fuels. 4. [Corrosion] - the term used when a metal (usually) is attacked by air, water or other substances in its surroundings. The more reactive a metal is, the more it corrodes e.g. iron corrodes in damp air while gold never corrodes. - Both oxygen and water are essential - Heat speeds up the process - Salt / sea water speeds up the process The following reaction types are not required in Chemical Reaction I -- so are provided here for interest only. 5. [Oxidation / Reduction] -- changing the electron structure of the compounds. 6. [Precipitation] -- formation of an insoluble solid when solutions are mixed. 7. [Displacement] -- changing one element (usually a metal) for another similar element in a compound. 8. [Neutralisation or acid/base reactions] -- changing the acidity of a solution 9. [Polymerisation] -- formation of very long molecules (e.g. plastics) from smaller compounds. 10. [Fermentation] -- production of alcohol using yeast. **Note:** Sometimes a reaction can be more than one type. For example, burning carbon in air to form carbon dioxide is combustion, oxidation [and] a synthesis reaction. ### **Activity 8: Reaction Types** A **DECOMPOSITION** reaction starts with one reactant and ends up with two or more products. Which of the following reactions are decomposition reactions? Circle the letters. {#a-decomposition-reaction-starts-with-one-reactant-and-ends-up-with-two-or-more-products.-which-of-the-following-reactions-are-decomposition-reactions-circle-the-letters..BodyText} ============================================================================================================================================================================== {#section-17.BodyText} a. **NaCl Na + Cl~2~** b. **Na + Cl~2~ NaCl** c. **H~2~O H~2~ + O~2~** d. **NaOH + HCl HOH + NaCl** e. **H~2~ + O~2~ H~2~O** A **SYNTHESIS** reaction starts with two reactants and ends up with one product. Which of the following reactions are synthesis reactions? Circle the letters. {#a-synthesis-reaction-starts-with-two-reactants-and-ends-up-with-one-product.-which-of-the-following-reactions-are-synthesis-reactions-circle-the-letters..BodyText} ============================================================================================================================================================== {#section-18.BodyText} f. **NaCl Na + Cl~2~** g. **Na + Cl~2~ NaCl** h. **H~2~O H~2~ + O~2~** i. **NaOH + HCl HOH + NaCl** j. **K +Cl~2~ KCl** 3. **A COMBUSTION reaction is burning in oxygen.** Which of the following reactions are combustion reactions? Circle the letters. k. **NaCl Na + Cl~2~** l. **CH~4~ + 2O~2~ CO~2~ + 2H~2~O** m. **2C~8~H~18~ + 25O~2~ 16CO~2~ + 18H~2~O** n. **Mg + O~2~ 2MgO** o. **H~2~O H~2~ + O~2~** 4. **A CORROSION reaction is when a metal reacts with oxygen to form a metal oxide and the metal is eaten away in the process. Which of the following reactions are corrosion reactions? Circle the letters.** p. **2Fe + 3O~2~ 2Fe~2~O~3~** q. **Na + HCl H~2~ + NaCl** r. **K + AgCl~2~ Ag + KCl** s. **KOH + HNO~3~ KNO~3~ + HOH** t. **2Mg +O~2~ 2MgO** **\ ** 5. **Balance these equations and identify the type of reaction.** **Type of reaction** 1. **\_\_HgO**  **\_\_Hg + \_\_O~2~ \_\_\_\_\_\_\_\_\_\_\_\_** 2. **\_\_ C~2~H~4~ + \_\_ O~2~** **\_\_CO~2~ + \_\_H~2~O \_\_\_\_\_\_\_\_\_\_\_\_** 3. **\_\_ Cl~2~ + \_\_ Ca**  **\_\_ CaCl~2~ \_\_\_\_\_\_\_\_\_\_\_\_** 4. **\_\_ C~2~H~6~ + \_\_ O~2~** **\_\_CO~2~ + \_\_H~2~O \_\_\_\_\_\_\_\_\_\_\_\_** 5. **\_\_ O~2~ + \_\_ Fe**  **\_\_ Fe~2~O~3~ \_\_\_\_\_\_\_\_\_\_\_\_** 6. **\_\_ Al + \_\_O~2~** **\_\_ Al~2~O~3~ \_\_\_\_\_\_\_\_\_\_\_\_** 7. **\_\_ S~8~ + \_\_ Fe**  **\_\_ FeS \_\_\_\_\_\_\_\_\_\_\_\_** 8. **\_\_ N~2~ + \_\_ H~2~** **\_\_ NH~3~ \_\_\_\_\_\_\_\_\_\_\_\_** 9. **\_\_ KClO~3~**  **\_\_ KCl + \_\_ O~2~ \_\_\_\_\_\_\_\_\_\_\_\_** 10. **\_\_ Mg + \_\_O~2~** **\_\_ MgO \_\_\_\_\_\_\_\_\_\_\_\_** **\ ** 6. Classify each of the following reactions as either synthesis, corrosion, decomposition or combustion u. hydrogen + oxygen water v. hydrogen peroxide hydrogen + water w. iron + water + oxygen iron (III) oxide x. glucose + oxygen carbon dioxide + water y. sodium + chlorine sodium chloride z. magnesium + oxygen magnesium oxide a. glucose Ethanol + carbon dioxide b. methane + oxygen carbon dioxide + water c. carbon + oxygen carbon dioxide d. silver chloride silver + chlorine e. sulfur + oxygen sulfur dioxide 7. Write the word equation for the rusting of iron 8. Can we describe rusting of iron as a combustion reaction? Explain. 9. For each of the following equations: a. b. c. d. i. ii. iii. iv. v. vi. vii. viii. ix. ### **Activity 9: Harder Balanced Equations** Write balanced chemical equations for each of the following reactions. \(a) The reaction of aqueous ammonia with iodine to form solid nitrogen triiodide and hydrogen. \(b) The combustion of propane gas (C~3~H~8~) to form carbon dioxide and water. \(c) The incomplete combustion of propane gas (C~3~H~8~) to form carbon monoxide and water. d. The reaction of solid copper oxide (CuO) with hydrogen gas to form copper metal and water. \(e) The reaction of hydrogen gas with chlorine gas to form hydrogen chloride (HCl) gas. \(f) The decomposition of liquid hydrogen peroxide (H~2~O~2~) to form oxygen gas and water. ### **Investigation: Mass Changes for Physical and Chemical** **Aim:** to find out whether mass is conserved in physical and chemical reactions. **Physical change 1: Dissolving salt in water** Substance name Mass (g) ---------------- ---------- Salt Water Salty water Conclusion: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Physical change 2: Melting ice** Record the mass of your beaker here: \_\_\_\_\_\_\_\_\_\_\_ g Substance name Mass (g) ---------------- ---------- Water Ice Conclusion: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Chemical reaction 1: Demo - Precipitation reaction between KI and lead nitrate** Substance name(s) Mass (g) ------------ ----------------------------------------------------------- ---------- Reactant 1 0.1 M Potassium iodide solution Reactant 2 0.01 M Lead (II) nitrate solution Products Potassium nitrate solution and solid lead iodide (yellow) Write a word equation for this reaction: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Conclusion: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ How could we find the mass of the solid lead iodide and potassium nitrate solutions separately? *(**Do NOT attempt this as LEAD IODIDE IS HIGHLY TOXIC**).* \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Chemical reaction 2: Displacement reaction between magnesium and copper sulfate solution** Substance name(s) Mass (g) ------------ ------------------- ---------- Reactant 1 Reactant 2 Products Write a word equation for this reaction: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Conclusion: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Chemical reaction 3: Thermal decomposition of copper carbonate into copper oxide and carbon dioxide gas** Substance name Mass (g) -------------------------- ---------- Copper carbonate (green) Copper oxide (black) Write a word equation for this reaction: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Your results will probably seem to show that the law of conservation of mass has been violated. Explain what is really happening. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Explain a test you could do to check whether your previous explanation is correct. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ What mass of carbon dioxide do you think was released in this reaction? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ ### **Investigation: Law of Conservation of Mass** **VERIFY** the conservation of mass in chemical reactions. -------------------------------------------------------------------------------------------------------- **USE** the conservation of mass to calculate the mass of products or reactants in chemical reactions. +-----------------------+-----------------------+-----------------------+ | #### Aim | | To determine how much | | | | oxygen reacts with | | | | magnesium | +-----------------------+-----------------------+-----------------------+ | #### Equipment | | Magnesium ribbon, | | | | crucible + lid, | | | | bunsen burner, | | | | heatproof mat, | | | | | | | | sand paper | +-----------------------+-----------------------+-----------------------+ | #### Method | | 1\. Clean a 4 cm | | | | strip of magnesium | | **Results:** | | with sand paper. | | | | | | | | 2\. Break the | | | | magnesium into | | | | small pieces and | | | | place them in a | | | | crucible and weigh. | | | | Record this weight | | | | below. | | | | | | | | 3\. Using a Bunsen | | | | burner, and a pipe | | | | clay triangle, heat | | | | the covered | | | | crucible strongly. | | | | You may need to | | | | leave the lid at an | | | | angle to let some | | | | oxygen in. | | | | | | | | **Warning:** **Do not | | | | look directly at the | | | | flame -- eye damage | | | | can occur**. | | | | | | | | 4\. When the | | | | reaction is | | | | finished, allow to | | | | cool. | | | | | | | | 5\. Reweigh the | | | | crucible and | | | | product. | | | | | | | | Weight of Mg + cruc | | | | ible before | | | | ------------------- | | | | ------------- -- | | | | Weight of Mg + cruc | | | | ible after | +-----------------------+-----------------------+-----------------------+ | #### Discussion / Que | | 1\. Describe the | | stions | | magnesium before | | | | burning. | | | | | | | | 2\. Describe the | | | | product formed. | | | | | | | | 3\. Write a balanced | | | | chemical equation | | | | for the reaction. | | | | | | | | 4\. Did the weight | | | | go up or down? | | | | Calculate the | | | | amount of oxygen | | | | that reacted. | | | | | | | | 5. How did you know | | | | that a chemical | | | | reaction took | | | | place? | +-----------------------+-----------------------+-----------------------+ | #### | |..................... | | | |..................... | | **Conclusion:** | |..................... | | | |............... | +-----------------------+-----------------------+-----------------------+ ### **Investigation: Factors that affect the corrosion of iron** ---------------------------------------------------------------------------------- **DESIGN** an experiment to investigate factors affecting the corrosion of iron. ---------------------------------------------------------------------------------- +-----------------------+-----------------------+-----------------------+ | #### Aim | | To investigate what | | | | factors affect the | | | | corrosion of iron | +-----------------------+-----------------------+-----------------------+ | #### Equipment | | Test tubes, paper | | | | clips or steel wool | | | | (in liu of iron | | | | nails), galvanised | | | | iron nails, salt | | | | solution, oil | | | | | | | | calcium chloride, | | | | stoppers | +-----------------------+-----------------------+-----------------------+ | #### Method | | 1\. Clean the nails | | | | with sand paper. | | | | | | | | 2\. Set up equipment | | | | as per table below. | | | | | | | | 3\. Choose one other | | | | experiment of your | | | | choice, and write | | | | the details below | | | | (e.g. steel wool in | | | | salt solution). | | | | | | | |..................... | | | |..................... | | | |..................... | | | |...... | | | | | | | |..................... | | | |..................... | | | |..................... | | | |...... | | | | | | | |  | +-----------------------+-----------------------+-----------------------+ | #### Safety: | |..................... | | | |..................... | | | |..................... | | | |...... | | | | | | | |..................... | | | |..................... | | | |..................... | | | |...... | +-----------------------+-----------------------+-----------------------+ **\ Results**: +-----------------------+-----------------------+-----------------------+ | #### Discussion / Que | | 1\. Which | | stions | | paperclips/steel | | | | wool tests rusted? | | | | | | | | 2\. Deduce which | | | | factors encourage | | | | rusting. | | | | | | | | 3\. Write a balanced | | | | chemical equation | | | | for the rusting of | | | | iron. | | | | | | | | 4\. Research what | | | | can be done to | | | | avoid rusting. | +-----------------------+-----------------------+-----------------------+ | #### | |..................... | | | |..................... | | **Conclusion:** | |..................... | | | |............... | | | | | | | |..................... | | | |..................... | | | |..................... | | | |............... | +-----------------------+-----------------------+-----------------------+ **\ ** **Practice Questions** ====================== Consider the following reaction: A. 12g B. 34g C. 56g D. 68g What is the symbol used to describe a compound dissolved in water? A. (dis) B. (s) C. (l) D. (aq) Which of the following is a chemical change? A. Sodium chloride dissolving in water B. Liquid nitrogen boiling C. Combustion of natural gas in air D. Liquid water freezing to become ice --------------------------- -- **Long Answer Questions** **Question 1** (3 marks) --------------------------- -- a. The reaction between hydrogen gas and oxygen gas. **1** b. The production of common table salt (NaCl) from its elements. **1** c. The combustion (oxidation) of carbon. **1** ------------------------- -- **Question 2** (2 mark) ------------------------- -- **2** -------------------------- -- **Question 3** (6 marks) -------------------------- -- +-----------------------------------+-----------------------------------+ | a. Mg~(\ s\ )~ + O~2(\ )~ → | | | MgO~(\ s\ )~ | | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | b. AgBr ~(\ s\ )~ → Ag~(\ )~ + | | | Br~2(\ l\ )~ | | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | c. Fe~(\ s\ )~ + O~2(\ g\ )~ → | | | Fe~2~O~3(\ )~ (Fe~2~O~3~ is | | | rust) | | +-----------------------------------+-----------------------------------+ -------------------------- -- **Question 4** (5 marks) -------------------------- -- **Name** **Formula** ------------------------ ------------- lithium sulfide Li~2~S magnesium chloride phosphorus trichloride aluminium oxide CaF~2~ CCl~4~ **5** -------------------------- -- **Question 5** (6 marks) -------------------------- -- **6** -------------------------- -- **Question 6** (2 marks) -------------------------- -- a. Write a word equation for the synthesis of sodium chloride. **1** b. Name the reactants in this reaction. **1** -------------------------- -- **Question 7** (6 marks) -------------------------- -- i. sulfur + oxygen sulfur dioxide **1** ii. magnesium + oxygen magnesium oxide **1** \(b) Write a balanced chemical equation for the following reaction, including all states. iron + hydrochloric acid (HCl) iron(II) chloride (FeCl~2~) + hydrogen **3** \(c) Balance the following chemical equation. Cu(NO~3~)~2(aq)~ + Na~2~CO~3(aq)~ NaNO~3(aq)~ + CuCO~3(s)~ **1\ ** -------------------------- -- **Question 8** (4 marks) -------------------------- -- **4** Notes: [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [\ ] Notes: [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [\ ] Summary of Chemical Reactions I ------------------------------- - A chemical change involves the rearrangement of atoms within the compounds, whereas a physical change usually simply involves a change of state or dissolving (i.e. compounds rearranging themselves in space -- BUT stay together as a compound). Ask yourself the question: can it be easily reversed -- if yes, it is a physical change. - Important types of reactions - Synthesis - the making of a compound from its elements. - Decomposition -- the breaking down of a compound into simpler substances - Combustion -- burning in oxygen gas (O~2~) producing heat - Corrosion -- slow reaction of metals usually with oxygen usually (water is also necessary for iron) - Naming/Formulae for **Elements** - For diatomics, gen-ine (H~2~, N~2~, O~2~, F~2~, Cl~2~, Br~2~, I~2~), use X~2~ followed by state. Only use diatomic when it is an element -- as soon as it reacts, forget diatomics. - For **all others**, use symbol (state). - Naming/Formulae for Compounds - Ionic compounds made from metals (on left hand side of periodic table) with a non-metal (on right) -- always consider valencies (swap and drop; reducing to LCD, but no 1's) to make up the formula (Group I is +1, II is +2, III is +3, V is -3, VI is -2, VII is -1) e.g. MgCl~2~. Order is 'metal non-metal' (changing NM suffix to --ide in name). No need for di, tri, etc in name. - Molecular compounds made from non-metals bonding with another non-metal -- never consider valencies. Use di, tri, tetra, penta, hexa to name and work out the formula. Mono- is used for the second chemical ONLY. Relate everything back to carbon dioxide if in doubt! - Exceptions are H~2~O -- water, NH~3~ -- ammonia; CH~4~ - methane - Word equations - Balancing equations - Write word equation, making sure you have considered all atoms. - Write correct formulae, THEN DON'T CHANGE THEM - Put numbers IN FRONT of formulae for balancing till numbers of ALL atoms is the same for each type of atom on both side of the equation. Remember that matter cannot be created nor destroyed -- Law of Conservation of Mass. - Add states (s), (l), (g) (Note: (aq) means dissolved in water). - If and only if you have trouble balancing, check your formulae are correct.
