Genie Chemie 4.2 CLIL Past Paper 2024-2025 - Part 1 PDF

CHAPTER 2 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025  Oxides LEARNING GOALS You already know …  How to classify substances into the correct substance class based on a given name or formula;  How to comp...

CHAPTER 2 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025  Oxides LEARNING GOALS You already know …  How to classify substances into the correct substance class based on a given name or formula;  How to compose a formula using oxidation numbers;  How to write the general formula of an oxide. You will learn …  To classify oxides into metal oxides and nonmetal oxides;  The properties and applications of oxides;  How to compose the formula of oxides;  How to name the oxides;  Which chemical reactions result in the formation of oxides. You may have heard about oxides before. For instance, last year you were introduced to the hazard symbol for oxidising substances. When iron oxidises, it forms an oxide. The properties of the resulting product differ from the original metal. 1 What is an oxide? When an element bonds to oxygen, an oxide is formed. An oxide can be formed through combustion. Oxides are binary compounds and are composed to 2 elements: a metal or nonmetal on the one hand and oxygen on the other hand. Oxygen is always the last element in the formula. Since the first element can be either a metal or a nonmetal, there will be two types of oxides: the metal oxides and nonmetal oxides, respectively. Since all substances have the element oxygen in common, oxygen is the functional group. Oxides are divided into: - Metal oxides: MO - Nonmetal oxides: nMO The metal oxides are ionic compounds given that they consist of a metal and a nonmetal. The nonmetal oxides are covalent compounds since they consist of two nonmetals. 20 _SECTION 01_  CHAPTER 2 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2 Metal oxides 2.1 Metals with only one possible oxidation number This type of metals can only form one oxide. Knowing the metal, you can easily compose the formula taking into account the neutral compound rule or the criss-cross rule. It is not necessary to name the number of ions of each element. The name only consists of the name of the metal ion followed by the suffix ‘oxide’. EXAMPLE FORMULA AND NAME OF A METAL WITH ONE OXIDATION NUMBER 1 The name and formula of the oxide of sodium (Na) HINT Sodium: +I because belongs to group Ia In the criss-cross rule, Oxygen: -II the charge of the first According to the neutral compound rule you need 2 sodium ions and element become the 1 oxygen ion: Na2O. index of the second You can also use the criss-cross rule: element and vice versa. If possible, you must simplify the indices. This results in: Na2O1 → Na2O The value of 1 can be omitted. If you can simplify the indices, you must do that. The formula unit is thus Na2O. The name is sodium oxide instead of sodium dioxide, because sodium has only 1 possible oxidation number. 2 The formula of aluminium oxide The name shows us that the formula will contain Al and O. Aluminium only has one possible oxidation number. Therefore we can form the formula using the neutral compound rule or the criss-cross rule. Aluminium: +III because belongs to group IIIa Oxygen: -II This results in the formula unit for aluminium oxide: Al2O3. This shows that you have to be cautious with names belonging to metal oxides containing metals with one possible oxidation number. Based on the name alone, it is not possible to derive the formula Al2O3. _SECTION 01_  CHAPTER 2 21 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 TASK 16 Write the formula and name of the requested metal that has 1 oxidation number. 1 Write the name and formula unit of the oxide of magnesium using the criss-cross rule. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ 2 What is the correct formula of lithium oxide? ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ 2.2 Metals with more than one possible oxidation number Metals with more than one possible oxidation number have more than one possible oxide. Therefore, it is important that the name carries extra information to make it clear which oxide you are referring to: - Either use the stock notation in which the oxidation number of the metal is mentioned between brackets without the plus or minus sign, and placed behind the name of the metal. Thus: metal (oxidation number) + oxide - Or use the systematic name in which the number of ions of each element is indicated using the Greek numerals. Thus: Greek numeral + metal Greek numeral + oxide 22 _SECTION 01_  CHAPTER 2 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES TASK 17 Practise writing the name of metal oxides containing a metal with multiple possible oxidation numbers. 1 Determine the formula of all possible oxides of iron (Fe). +II +III Criss-cross rule Formula unit Stock notation Systematic name 2 Write the formula unit using the criss-cross rule and the systematic name of lead(II) oxide. _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ 3 What is the stock notation of dicopper oxide? a First write the formula unit: _________________________________________________________ b Calculate the oxidation number of copper in this substance: _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ c Write the stock notation of this substance: ____________________________________________ 23 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 3 Nonmetal oxides Nonmetal oxides are covalent compounds of which the elements can combine in different ratios. You always write the systematic name with the Greek numeral that shows the number of atoms of each element present in the substance: Greek numeral + nonmetal Greek numeral + oxide TASK 18 Write down the name and formula of all oxides of chlorine (Cl). +I +III +V +VII Criss-cross rule Formula Systematic name - Oxides are binary compounds: they consist of a metal or a nonmetal and oxygen. There are 2 types of oxides: Metal oxides: MO Nonmetal oxides: nMO - The functional group is oxygen. - Metal oxides: → metals with one possible oxidation number: Formula: look up the charge on the PTE + apply criss-cross rule Name: metal + oxide → metals with more than one possible oxidation number: Formula: since there are mulitple possibilities, the oxidation number must be supplied. Systematic name: Greek numeral + metal + Greek numeral + oxide - Stock notation: Metal (oxidation number) + oxide 24 _SECTION 01_  CHAPTER 2 _SECTION 01_  CHAPTER 2 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES - Nonmetal oxides: Formula: multiple possibilities, information about the oxidation number must be supplied. Always use the systematic name: Greek numeral + nonmetal + Greek numeral + oxide  Make exercises 10 to 15 on p. 68-69. 4 Use and applications of oxides You may not be aware that you are surrounded by oxides. Scan the QR- code and discover the most important applications of oxides. One of the best known oxides is without doubt carbon dioxide or carbonic acid gas CO2. It is an important greenhouse gas that is produced during the combustion of fossil fuels. It is also used in carbonated drinks. Maybe you have a device at home to make sparkling water or lemonade. This device contains carbon dioxide under high pressure. Fig. 6: Carbon dioxide is produced during combustion processes. Carbon dioxide is also sometimes used in fire extinguishers. Carbon dioxide has a higher density than air, it is heavier than oxygen and will replace oxygen around the burning substance. It will extinguish the fire as there is no more oxygen to feed the flames. If carbon dioxide is cooled to such extent that it becomes solid, it is called dry ice. It is used as a cooling agent, or for special effects during shows or in cocktails. However, be careful when handling dry ice. As mentioned before, Fig. 7: Carbon dioxide under carbon dioxide is heavier than air, so when large amounts of CO2 are being the form of dry ice. released you can die from a lack of oxygen. _SECTION 01_  CHAPTER 2 25 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 When fossil fuels are combusted in oxygen-poor environments, for instance if the chimney is not allowing enough air (and therefore oxygen gas) to pass, the very toxic gas carbon monoxide CO is formed. Since this gas is colourless and odourless, it is often called the silent killer. Unfortunately, many people die from CO-poisoning in Belgium every year. Another well-known oxide is dinitrogen oxide N2O or laughing gas. This Fig. 8: Chimneys need to be substance is used, among others, in whipped cream dispensers and to cleaned regularly. increase the power of an engine (see the TV series ‘Fast and Furious’). Fig. 9: Whipped cream Fig. 10: Nitrous bottles to increase the Fig. 11: Fast car in Fast and Furious dispenser. power of car engines DID YOU KNOW … Laughing gas was often used as a sedative, although more recently is has been mainly abused: it is used as a drug and very dangerous. For that reason, the sale of laughing gas to minors has been forbidden since March 5th 2021. Scan the QR-code and watch the campaign ‘Rij ballonvrij’ from the Netherlands about the dangers of laughing gas. When you read the ingredient list of food items, it will often list some E- numbers. For instance, E220 refers to sulphur dioxide SO2. It is added to raisins or dried apricots, amongst others. Fig. 12: Sulphur oxide in dried apricots. 26 _SECTION 01_  CHAPTER 2 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES A solid metal oxide that, unfortunately, forms very easily, is diiron trioxide or rust Fe2O3. As soon as water and air are in touch with an iron object, it will start rusting. The metal loses its properties such as strength and pliability. The substance become very fragile and will pulverise easily. Fig. 13: Rust is a solid metal oxide. Another common solid metal oxide is calcium oxide or quicklime CaO. It was used to mark the lines on football fields (although that is forbidden now). It was also used to speed up the decomposition process of decomposing bodies. Fig. 14: Chalk lines on a football field. DID YOU KNOW… In the city of Mainz in western Germany, archaeologist have lifted the lid of a 1000 year old sarcophagus. It contained the remains of a person, possibly a cleric from the 11th century. The scientists suspect that the deceased person was covered with quicklime to speed up the decomposition of the body. Source: Het Laatste Nieuws. TASK 19 Exercise your knowledge of oxides using your flash cards. _SECTION 01_  CHAPTER 2 27 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 Formula Systematic name Stock Trivial Application / notation name properties CO2 Carbon dioxide / carbonic Fire extinguishers acid gas Carbonated drinks N2O Dinitrogen oxide / laughing Anaesthesia gas Fe2O3 Diiron trioxide Iron(III) oxide rust Rusting of iron SO2 Sulphur dioxide / Preservative CO Carbon monoxide / Product of incomplete combustion, toxic CaO Calcium oxide / quicklime /  Make exercise 16 on p. 69. 5 Reaction patterns 5.1 Formation of metal oxides TASK 20 DEMO Your teacher investigates which substance will form during the combustion of a metal. Method Your teacher takes a piece of magnesium ribbon using tongs and combusts it. Then, your teacher will add a bit of water containing universal indicator solution. Observations __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ Conclusion __________________________________________________________________________________ __________________________________________________________________________________ 28 _SECTION 01_  CHAPTER 2 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES The reaction pattern is a general description of the substance classes of the substances participating in the reaction (reactants and reaction products). It does not contain specific substances except for oxygen gas, water,…. The coefficients cannot be adjusted. - Reaction pattern: metal + oxygen gas → metal oxide (M) + (O2) → (MO) The reaction equation shows the specific substances. In the reaction pattern, the coefficients need to be adjusted to balance the reaction. - Reaction equation: 2 Mg + O2 → 2 MgO 5.2 Formation of nonmetal oxides TASK 21 DEMO Your teacher investigates which substance is produced during the combustion of a nonmetal. Method Your teacher takes an old glass jar with plastic lid and puts a combustion spoon through the lid by heating up the back-end of the combustion spoon. Then, a little bit of water containing universal indicator solution is added to the jar. Your teacher fills the combustion spoon with sulphur, lights the sulphur and holds the burning sulphur above the water surface. Then, the jar is closed. Observations __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ Conclusion __________________________________________________________________________________ __________________________________________________________________________________ _SECTION 01_  CHAPTER 2 29 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 - Reaction pattern: Nonmetal + oxygen gas → nonmetal oxide nM + O2 → nMO - Reaction equation: S8 + 8 O2 → 8 SO2 The reaction pattern is a general description of the substance classes of the substances participating in the reaction (reactants and reaction products). - Reaction pattern of the formation of metal oxides: Metals + oxygen gas → metal oxides M + O2 → MO - Reaction pattern of the formation of nonmetal oxides: Nonmetals + oxygen gas → nonmetal oxides nM + O2 → nMO  Make exercises 17 to 19 on p. 69. 30 _SECTION 01_  CHAPTER 2  CHAPTER 3 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES  Hydroxides LEARNING GOALS You already know …  How to classify inorganic substances into the correct substance class based on a given name or formula;  How to write a formula using oxidation numbers;  How to name the oxides and how to write their formulas;  How to write the general formula of hydroxides. You will learn …  The properties and applications of hydroxides;  How to write the formula of hydroxides;  How to name hydroxides;  Which chemical reactions result in the formation of hydroxides. In this chapter we will learn more about hydroxides. The hydroxides were already briefly explained in chapter 1. 1 What is a hydroxide? A hydroxide is a compound consisting of a metal and one or more hydroxide groups (OH--groups). All hydroxides are ionic compounds. The functional group is the hydroxide ion: OH-. The charge on the hydroxide ion is -I, given that oxygen has an oxidation number of -II while hydrogen has an oxidation number of +I. The general formula of a hydroxide is MOH. The index of the metal is always 1. Instead of a metal ion, you can also use the ammonium ion (NH4+). DID YOU KNOW … Hydroxides are ionic compounds, but have a covalent bond as well. The bond between metal and oxygen is a bond between a metal and a nonmetal, which is an ionic bond. However, oxygen is also bonded to hydrogen. These are two nonmetals, which form a covalent bond. _SECTION 01_  CHAPTER 3 31 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 2 Formula and nomenclature The composition of formulas and names are analogous to the ones of metal oxides. 2.1 Metals with one possible oxidation number For hydroxides that contain the ammonium ion or a metal with only 1 possible oxidation number, you can form the formula by applying the criss- cross rule after looking up the oxidation number on the PTE. The nomenclature is: metal (or ammonium) + hydroxide. TASK 22 Practise writing names and formulas of hydroxides. 1 Write the name and formula unit of the hydroxide of magnesium using the criss-cross rule. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 2 Write the name and formula unit of the hydroxide of ammonium using the criss-cross rule. _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ 32 _SECTION 01_  CHAPTER 3 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2.2 Metals with more than one possible oxidation number Like the oxides, you can write more than one hydroxide with the same metal if the metal has more than one possible oxidation number. For the nomenclature, you use either the systematic name or the stock notation. TASK 23 Practise writing the name and formula of hydroxides. 1 Complete the table of the hydroxides of copper. +I +II Criss-cross rule Formula unit Stock notation Systematic name 2 What is the stock notation of lead tetrahydroxide? a First write the formula unit: ________________________________________________________ b Calculate the oxidation number of lead in this substance: ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ c Write down the stock notation: _____________________________________________________ _SECTION 01_  CHAPTER 3 33 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 - Hydroxides are ionic compounds between a metal ion (or the ammonium ion) and the hydroxide ion. - The hydroxide ion is the functional group and has an oxidation number of -I: OH- - NH4+ = ammonium ion - If the metal has only 1 possible oxidation number: Formula: look up the charge on the PTE + apply criss-cross rule Name: metal (or ammonium) + hydroxide - If the metal has more than one possible oxidation number: Formula: since there are multiple possibilities, the oxidation number must be provided. Systematic name = metal + Greek numeral + hydroxide Stock notation = Metal (oxidation number) + hydroxide  Make exercises 20 to 25 on p. 69-70. 3 Use and applications of hydroxides In daily life, hydroxides are often used for cleaning. Sodium hydroxide, caustic soda or lye NaOH is a strong drain cleaner. A solution of sodium hydroxide will dissolve hair and soap. You have to be very careful when using this substance. It is very corrosive and can cause burns. A special substance is ammonia NH3. When ammonia dissolves in water, ammonium hydroxide NH4OH is formed. The dissolution of ammonia is discussed in section 4. The solution is known for its degreasing properties and is used, for instance, for cleaning windows. The substance has a penetrating smell. Be careful because it can irritate your mucous membranes. The same Fig. 15: Drain cleaner contains penetrating smell can be noticed in stables. Indeed, ammonia is a component ammonium hydroxide. of dung. Some lab experiments will require the use of calcium hydroxide or slaked lime or lime water Ca(OH)2. This solution can be used to prove the presence of carbon dioxide. Note that the water coming from your tap at home is water rich in lime, but that is not the same as lime water! Fig. 16: Ammonia has degreasing properties. 34 _SECTION 01_  CHAPTER 3 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES TASK 24 DEMO Your teacher investigates which substance will form when you mix carbon dioxide with lime water. Method Your teacher makes a solution of lime water by dissolving calcium oxide in water. About 2 mL of this solution is added to a test tube. Your teacher will then carefully blow into the solution with a straw. Observations __________________________________________________________________________________ Conclusion When you mix lime water with carbon dioxide, a ________________________________________ is formed. You can prove the presence of carbon dioxide using lime water. Formula Systematic name Trivial name Application / properties Ca(OH)2 calcium hydroxide slaked lime Indicator of carbon dioxide NaOH sodium hydroxide lye / caustic soda Drain cleaner NH4OH ammonium hydroxide ammonia Degreaser  Make exercise 26 on p. 71. TASK 25 Exercise your knowledge of hydroxides using your flash cards. _SECTION 01_  CHAPTER 3 35 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 4 Reaction pattern During the experiment with lime water, we made our own lime water by dissolving calcium oxide in water: - Reaction pattern: Metal oxide + water → hydroxide MO + H2O → MOH - Reaction equation: CaO + H2O → Ca(OH)2 TASK 26 In task 20 we observed that a universal indicator solution turns blue when adding magnesium oxide. What is the pH linked to this colour? _______________________________________________________ - Reaction pattern: metal oxide (MO) + water (H2O) → hydroxide (MOH) - Reaction equation: MgO + H2O → Mg(OH)2 Since the reaction between a metal oxide and water results in the formation of a hydroxide, metal oxides are also called basic oxides (see chapter 5). Reaction pattern of the formation of hydroxides: metal oxide + water → hydroxide MO + H2O → MOH Metal oxides are basic oxides.  Make exercises 27 to 29 on p. 71. 36 _SECTION 01_  CHAPTER 3  CHAPTER 4 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES  Acids LEARNING GOALS You already know …  How to classify inorganic substances into the correct substance class based on a given name or formula;  How to classify inorganic substances based on the colour of an indicator;  How to write a formula using oxidation numbers;  How to name the oxides and hydroxides and how to write their formulas.  How to write the general formula of acids. You will learn …  To name an acid when the formula is given and vice versa  To classify acids into binary and ternary acids;  The properties and applications of acids;  To write the formula of binary and ternary acids;  How to name binary and ternary acids;  Which chemical reactions result in the formation of binary and ternary acids. You may have eaten something acidic before: a slice of lemon or a sour candy. You are not allowed to taste substances during a chemical practicum, and for that reason we learned other ways to determine if a substance is an acid or not. In this chapter we will learn more about acids. 1 What is an acid? An acid consists of a hydrogen atom and an acid radical. The hydrogen atom is the functional group. The acid radical can be a nonmetal or a nonmetal combined with one or more oxygen atoms. The general formula of an acid is HA. Since all acids have a fixed formula, the index of the hydrogen atom never has to be mentioned in the name. Acids are divided into 2 groups, depending on the composition of the acid radical. 1 Acids of which the acid radical consists of a nonmetal are called binary acids (they consist of two elements). The general formula of a binary acid is HnM. 2 Ternary acids, on the other hand, are acids of which the acid radical consists of a nonmetal and oxygen. The general formula of a ternary acids is HnMO. Both binary as ternary acids consist solely of nonmetals. All acids are covalent compounds. Since the acid radical is an important part of salts as well, we will study the acid radicals in detail in this chapter. _SECTION 01_  CHAPTER 4 37 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 2 Binary acids A binary acid consists of 2 elements: the hydrogen atom and a nonmetal. HA or HnM is the general formula of a binary acid. All nonmetals carry their lowest oxidation number in the binary acids. This is a very convenient way to derive the formula of acids. TASK 27 Determine the formula of the binary acid of sulphur. _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ The name of binary acids is composed of: hydrogen + abbreviated Latin name of the nonmetal + suffix ‘ide’. The formula of acids is fixed, therefore Greek numerals are never used. The acid radical is an important part of salts as well. You can form an acid radical by removing the hydrogen ions (H+) from the formula of the corresponding acid. For each hydrogen ion that you remove, the charge on the acid radical will be lowered by 1. Example: HCl - 1 H+ → Cl- H2S - 2 H+ → S2- The name of the acid radical is analogous to that of the acid itself, except that the hydrogen atoms are not mentioned because they have been removed. The name of the acid radical consists of the abbreviated Latin name of the nonmetal + suffix ‘ide’. The extra suffix ‘-ion’ refers to the fact that the particle is charged and that the compound is not yet complete: the formula needs to be completed using a positive particle. 38 _SECTION 01_  CHAPTER 4 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES It is very important to know the acid radicals by heart: Molecular Systematic name Acid radical Name acid radical formula HF hydrogen fluoride F- fluoride ion HCl hydrogen chloride Cl- chloride ion - HBr hydrogen bromide Br bromide ion HI hydrogen iodide I- iodide ion 2- H2S hydrogen sulphide S sulphide ion Table 4: Binary acids and binary acid radicals. There is one binary acid of which you have to know the trivial name. The trivial name of hydrogen chloride is hydrochloric acid. 3 Ternary acids The name already reveals that the ternary acids consist of three different elements. Apart from hydrogen, it also contains a nonmetal, and minimum one oxygen atom. The general formula of a ternary acid is HnMO. The functional group is again the hydrogen atom. Ternary acids can be divided into the main acids, which are the most common acids, and the acids derived from the main acids. The number of hydrogen and oxygen atoms in the formula cannot be derived from the PTE or from their name. You have to learn the formulas of these acids by heart! In case of main acids, the oxidation number of the nonmetal equals the group number, except for the halogens. Here, the oxidation number is not +VII, but +V. EXAMPLE H2CO3 HClO3 OG(C) = +IV OG(Cl) = +V The name of the main acids is analogous to the one of the binary acids, except for the suffix which is not ‘-ide’ but ‘-ate’: hydrogen + abbreviated Latin name + ‘-ate’. The acid radical is formed analogous to the one of the binary acids. You remove one or more hydrogen ions from the formula. Per hydrogen ion that is removed, the charge on the acid radical will be lowered by 1. In the name, ‘hydrogen’ is removed, while ‘ion’ is added to show that the particle is charged. _SECTION 01_  CHAPTER 4 39 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 It is very important to know the acid radicals really well, since we need them to form salts. Molecular Systematic name Trivial name Acid Name acid formula radical radical H2CO3 hydrogen carbonate carbonic acid CO32- carbonate ion HNO3 hydrogen nitrate saltpetre / nitric acid NO3- nitrate ion H3PO4 hydrogen phosphate phosphoric acid PO43- phosphate ion H2SO4 hydrogen sulphate sulphuric acid SO42- sulphate ion HClO3 hydrogen chlorate chloric acid ClO3- chlorate ion HBrO3 hydrogen bromate bromic acid BrO3- bromate ion HIO3 hydrogen iodate iodic acid IO3- iodate ion Table 5: Ternary acids and ternary acid radicals. Last year you learned how to draw Lewis structures. The Lewis structure of carbonic acid is as follows: Fig. 17: Lewis structure of carbonic acid. Several ternary acids have acids derived from them. The formula is similar to the one of the main acid, except for the number of oxygen atoms. We only discuss two of the acids with derived forms: Molecular Systematic name Trivial name Acid Name acid radical formula radical HNO2 hydrogen nitrite nitrous acid NO2- nitrite ion H2SO3 hydrogen sulphite sulphurous acid SO32- sulphite ion Table 6: Ternary acids and their derived forms. These formulas each have exactly one oxygen atom less than the corresponding main acid. When a ternary acid has one oxygen atom less than the main acid, the name will end on ‘-ite’ instead of ‘-ate’. In the trivial names, the name will end on ‘-ous’ instead of ‘-ic’. 40 _SECTION 01_  CHAPTER 4 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES A binary acid: - Consists of 2 elements: the hydrogen atom and a nonmetal. - The oxidation number of the nonmetal is as low as possible, namely the group number – 8. - The name is formed by hydrogen, followed by the abbreviated Latin name of the nonmetal, and ending with -ide. - The trivial name of hydrogen chloride is hydrochloric acid. - The acid radical is formed by removing one or more hydrogen ions from the formula of the acid. Per hydrogen ion that is removed, the charge on the acid radical will be lowered by 1. - The binary acids and acid radicals that need to be known by heart are: Formula Systematic name Acid radical Name acid radical HF Hydrogen fluoride F- Fluoride ion HCl Hydrogen chloride Cl- Chloride ion HBr Hydrogen bromide Br - Bromide ion HI Hydrogen iodide I- Iodide ion 2- H2S Hydrogen sulphide S Sulphide ion A ternary acid: - Consists of hydrogen, a nonmetal, and one or more oxygen atoms. - The name of the main acid is formed by hydrogen, followed by the abbreviated Latin name of the nonmetal, and ending with -ate. - The main acids and acid radicals that need to be known by heart are: Molecular Systematic Trivial name Acid Name acid formula name radical radical H2CO3 Hydrogen Carbonic acid CO32- carbonate carbonate ion - HNO3 Hydrogen Saltpetre / NO3 nitrate ion nitrate Nitric acid H3PO4 Hydrogen Phosphoric acid PO43- Phosphate phosphate ion H2SO4 Hydrogen Sulphuric acid SO42- Sulphate ion sulphate HClO3 Hydrogen Chloric acid ClO3- Chlorate ion chlorate HBrO3 Hydrogen Bromic acid BrO3- Bromate ion bromate HIO3 Hydrogen Iodic acid IO3- Iodate ion iodate _SECTION 01_  CHAPTER 4 41 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 - The acids derived from the main acids and their acid radicals: Molecular Systematic Trivial name Acid Name acid formula name radical radical HNO2 Hydrogen Nitrous acid NO2- nitrite ion nitrite H2SO3 Hydrogen Sulphurous acid SO32- Sulphite ion sulphite  Make exercises 30 to 33 on p. 71-72. 4 Use and applications of acids The acid present in your stomach is hydrochloric acid or hydrogen chloride HCl. Its purpose is to help with the digestion of food. Hydrochloric acid is very corrosive. You can best notice this when you have to throw up regularly, or when the valve between your stomach healthy stomach reflux and oesophagus is not working well. Your stomach is protected from the acid by its Fig. 18: Hydrochloric acid in the stomach helps with the digestion of mucus layer, but your oesophagus can be food. Reflux is a condition in which the seriously damaged by it. acidic stomach contents flow into the oesophagus. The gas escaping during volcanic eruptions is hydrogen sulphide or H2S. You may have already smelled it in rotten eggs or stink Fig. 19: Toxic hydrochloric acid fumes during a bombs. volcanic eruption. DID YOU KNOW… During the volcanic eruption on La Palma in 2021, people were warned about toxic hydrochloric acid fumes. When lava with a temperature of 1000 °C comes in contact with seawater, it can produce toxic vapours. This chemical reaction may result in the formation of a hydrochloric acid gas cloud. This phenomenon is known as ‘laze’, a combination of ‘lava’ and ‘haze’. The toxic vapours can cause breathing and skin problems. Source: De Standaard 42 _SECTION 01_  CHAPTER 4 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES Carbonic acid or hydrogen carbonate H2CO3 is probably the best known acid amongst the ternary acids. This acid is formed when carbon dioxide dissolves in water. You may have heard about sulphuric acid or hydrogen sulphate H2SO4 before. It is present in car batteries and is, unfortunately, best known Fig. 20: Sparkling water for its highly corrosive properties. Newspapers contains carbonic acid. have reported about people that are horribly disfigured by a sulphuric acid attack. The substance is strongly hygroscopic. This means that it readily attracts water from its surroundings. It attracts water to such extent that it removes all water from your cells causing terrible burns. Fig. 21: Sulphuric acid causes severe burns. ! SAFETY SHEET If you have to mix sulphuric acid and water in the lab, you always have to add sulphuric acid last. Never add water to sulphuric acid! This rule can easily be memorised by the following mnemonic: ‘never baptise sulphuric acid’. Fig. 22: Sulphuric acid should never be baptised. Coke is the only soft drink that contains phosphoric acid or hydrogen phosphate H3PO4 next to carbonic acid. Fig. 23: Four photos of the same wisdom tooth: upper left the tooth in its original state, upper right the tooth after submersing in cola for one day, lower left is after submersing in cola for one week and lower right after submersing in cola for one month. The phosphoric acid in cola affects the tooth enamel while the colourants cause the root to turn brown. _SECTION 01_  CHAPTER 4 43 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 TASK 28 Exercise your knowledge of acids using your flashcards. Molecular Systematic name Trivial name Application formula H3PO4 Hydrogen phosphate Phosphoric acid Present in coke H2CO3 Hydrogen carbonate Carbonic acid Soft drink HCl Hydrogen chloride Hydrochloric acid Stomach H2SO4 Hydrogen sulphate Sulphuric acid - Car battery - Do not baptise!  Make exercise 34 on p. 72. 5 Reaction patterns A binary acid can be formed through the reaction of a nonmetal and hydrogen gas. - Reaction pattern: Nonmetal + hydrogen gas → binary acid nM + H2 → HnM - Reaction equation: Cl2 + H2 → 2 HCl A ternary acid can be formed through the reaction of a nonmetal oxide and water. For this reason nonmetal oxides are called acidic oxides. - Reaction pattern: Nonmetal oxide + water → ternary acid nMO + H2O → HnMO - Reaction equation: CO2 + H2O → H2CO3 44 _SECTION 01_  CHAPTER 4 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES TASK 29 In task 21 we saw that a universal indicator solution turns orange-red after adding the combustion gasses of octasulphur. What is the pH corresponding to this colour? ________________________________________________ Reaction patterns of the formation of acids: - Nonmetal + hydrogen gas → binary acid nM + H2 → HnM - Nonmetal oxide + water → ternay acid nMO + H2O → HnMO → Nonmetal oxides are acidic oxides.  Make exercises 35 to 37 on p. 72-73. _SECTION 01_  CHAPTER 4 45  CHAPTER 5 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025  Acidity of a solution LEARNING GOALS You already know …  How to classify inorganic substances into the correct substance class based on a given name or formula;  How to use indicators to identify the substance class of inorganic substances;  How to write a formula using oxidation numbers;  How to name the oxides, hydroxides and acids and how to write their formulas; You will learn …  To discuss the concept of acidity and pH of a solution using examples;  To link the concepts acidic, basic and neutral to the pH or acidity of a solution;  How to determine the pH or acidity of a solution experimentally;  What buffer solutions are used for. In chapter 1 we used indicators to classify inorganic substances into their substance classes. This chapter focusses on these indicators. 1 pH and acidity of a solution Fig. 24: The pH scale. The pH scale ranges from 0 to 14. The lower the pH, the more acidic the solution. A solution with a high pH is a called a basic solution. The counterpart of an acid in chemistry is not sweet or salty, but basic! 46 _SECTION 01_  CHAPTER 5 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES A solution with a pH value of 7 is a neutral solution: this solution is neither acidic nor basic. Remark that the acidity of a solution and the pH are inversely proportional to each other: the more acidic the solution, the higher the acidity, and the lower the pH. In the past, the acidity of a solution was determined by tasting the solution. A solution with a low pH tastes acidic while a solution with a high pH has a soapy taste. Last year, you learned that it is forbidden to taste solutions in the lab because it can be dangerous. Moreover, it is far from accurate. For Fig. 25: Coca Cola has a pH of 2.4. A soft drink with a pH < 4 can erode tooth instance, the pH of Coca Cola is 2.4 but it enamel. does not taste acidic. This is due to the large amounts of sugar or sweeteners added to Coca Cola. TASK 30 Why is it not recommended to taste a solution to determine if it is basic or acidic? Give two arguments. - ___________________________________________________________________________________ ___________________________________________________________________________________ - ___________________________________________________________________________________ ___________________________________________________________________________________ TASK 31 PRACTICUM Investigate if a solution is acidic, basic or neutral. Execute the lab. You can find the information on. DID YOU KNOW… Light soft drinks cause as much erosion of your teeth as regular soft drinks because they contain equal amounts of acid. However, they contribute less to tooth decay. At which pH will your tooth enamel start to erode? Tooth enamel will start to dissolve if the pH value in your mouth is lower than 5.5. The more acidic the drink, the faster the enamel will erode. A soft drink with a pH lower than 4 can erode tooth enamel. _SECTION 01_  CHAPTER 5 47 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2024-2025 1.1 pH indicators An easy way to determine if a solution is basic or acidic, is by using pH indicators. These substances are often present in nature and change colour depending on the acidity of the solution. Red cabbage juice is a pH indicator that you can easily make yourself. You can either boil some pieces of red cabbage or crush some pieces in a bit of water using pestle and mortar. The water will quickly turn blue-purple. When you add a few drops of lemon juice (an acid), the colour will change to red. When you add a few drops of sodium hydroxide solution (a base), the colour will change to green/yellow. The results of the experiments with other indicators are shown in the table: pH indicator Colour in acidic Colour in neutral Colour in basic environment environment environment Red cabbage juice Red Blue-purple Green-yellow Methyl orange Red Yellow Yellow Litmus Red Red-blue Blue Phenolphthalein Colourless Colourless Fuchsia Bromothymol blue Yellow Green Blue You may have come across indicators in daily life. When preparing red cabbage, you often add a drop of vinegar to the purple red cabbage. As a result, the dish colours red. Likewise, hortensias will have a different colour depending on the acidity of the soil. It is not uncommon for pink hortensias Fig. 26: Hortensias can change to turn blue after some years, due to the soil becoming more acidic. colour depending on the acidity of the soil. Although colour indicators are easy to use, they have the disadvantage that you cannot distinguish between two acidic solutions: a solution with a pH value of 1 and one with a pH value of 2 will produce the same colour. You can easily solve this by making a mixture of different indicators. You can use pH strips to check the acidity of swimming pool water. These strips are filter paper that has been submersed in a solution of universal Fig. 27: A universal indicator indicator. Alternatively, you can use a universal indicator solution and solution can be used to determine the pH of a solution. compare the colour of the solution to the colour given on a colour scale. 1.2 pH meter Some applications (mainly in the lab) require an accurate determination of the pH. You can easily do this using a pH meter. Once the electrode is in the solution you can quickly and accurately determine the pH. A pH meter has to be calibrated regularly. This is accomplished using a buffer solution. Fig. 28: A pH meter. 48 _SECTION 01_  CHAPTER 5 2024-2025 SECTION 1 ⁞ INORGANIC SUBSTANCE CLASSES 2 Buffer You may have heard about buffers in a different context. For instance, in football where they have buffer zones in the stadium. This is an empty zone separating rivaling groups of football fans. Buffers are also used in economy. Here, a buffer means a financial reserve. In a chemical context, a buffer refers to a solution of which the pH value stays within certain limits, even when adding other substances (an acid, a base, water). Buffer solutions are very important, because many chemical and biological processes have an ideal pH value at which they operate. Due to ongoing acidification of the environment, natural buffer systems are under a lot of pressure. Oceans are acidifying, as a results of which many organisms are struggling to survive, coral reefs are starting to dissolve … Fig. 29: Lens solutions contain Most contact lens solutions contain a buffer that keeps the pH value between a buffer. 7.2 and 7.4, the pH value at which the solution works best. To avoid eye irritation, the pH should not differ too much from the pH of tears. Therefore, the pH value should stay between 6.6 and 7.8. Buffers are also used to calibrate pH meters. For this you need a buffer solution with a low pH and one with a high pH. You measure the pH of both solutions after which a calibration curve is made. It is very important to use solutions of which the pH does not change, in case some drops of water or Fig. 30: pH meter are calibrated any other substance are accidentally added (such as drops clinging to the pH using buffer solutions. electrode). DID YOU KNOW… - The more acidic the solution, the higher the acidity and the lower the pH The pH of blood of of the solution. healthy people ranges - The pH scale ranges between 0 and 14: between 7.35 and 7.45. A solution with a pH < 7 is an acidic solution Both lungs and kidneys A solution with a pH = 7 is a neutral solution are involved in the A solution with a pH > 7 is a basic solution regulation of the acidity - You can determine the pH using pH indicators: these substance change of blood. colour depending on the pH or acidity of the solution. Hyperventilating causes - A pH meter is a digital and very accurate way to determine the pH of a a change in the pH of solution. blood. Also acute - A buffer is a solution of which the pH change is rather stable, even after diarrhoea or vomiting adding small amounts of acid or hydroxide. can affect the pH of  Make exercises 38 to 47 on p. 73-75. your body. _SECTION 01_  CHAPTER 5 49