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Questions and Answers

Explain why Group I elements are more reactive than transition elements.

Group I elements have only one electron in their outer shell, which they readily lose to form stable ions, whereas transition elements have more electrons in their outer shells and higher nuclear charge, making them less reactive.

Describe how you can distinguish between a saturated solution and an unsaturated solution.

If adding more solute dissolves, the solution is unsaturated. If adding more solute does not dissolve and it settles at the bottom, the solution is saturated.

Explain why ionic compounds, such as lithium chloride, have high melting points.

Ionic compounds have strong electrostatic forces of attraction between oppositely charged ions, requiring a lot of energy to overcome, leading to high melting points.

Explain, in terms of electron arrangement, why chlorine is more reactive element than iodine.

<p>Chlorine has fewer electron shells compared to iodine, so its outer electrons are more strongly attracted to the nucleus. This makes it easier for chlorine to gain an electron during reactions, increasing its reactivity.</p>
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Explain why transition elements can form multiple stable oxidation states, unlike Group I elements.

<p>Transition elements have partially filled d-orbitals, allowing them to lose varying numbers of electrons from both the s and d orbitals. Group I elements readily lose their single outer electron, resulting in only one stable oxidation state.</p>
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Describe how you would test for the presence of chloride ($Cl^−$) ions in a solution.

<p>Add dilute nitric acid ($HNO_3$) followed by silver nitrate ($AgNO_3$) solution. A white precipitate indicates the presence of chloride ions.</p>
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Explain why graphite, a form of carbon, conducts electricity while diamond, another form of carbon, does not.

<p>Graphite has a layered structure with delocalized electrons that can move freely between layers, allowing it to conduct electricity. Diamond has a tetrahedral structure with all electrons involved in covalent bonds, so there are no free electrons to carry charge.</p>
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Describe how you would prepare a standard solution of 250 $cm^3$ of 0.1 mol/$dm^3$ sodium carbonate ($Na_2CO_3$).

<p>Weigh 2.65g of $Na_2CO_3$, dissolve it in distilled water in a 250 $cm^3$ volumetric flask, and then add more distilled water until the solution reaches the 250 $cm^3$ mark.</p>
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Explain, using collision theory, how increasing the concentration of reactants increases the rate of reaction.

<p>Increasing the concentration of reactants increases the number of reactant particles per unit volume. This leads to more frequent collisions between reactant particles, increasing the rate of successful collisions and, therefore, the rate of reaction.</p>
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Explain why increasing the temperature generally increases the rate of a chemical reaction.

<p>Increasing the temperature increases the average kinetic energy of reactant particles, causing more frequent and energetic collisions. This increases the number of collisions that exceed the activation energy, leading to a higher rate of reaction.</p>
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Describe how a catalyst increases the rate of a chemical reaction.

<p>A catalyst provides an alternative reaction pathway with a lower activation energy. This allows more reactant particles to have sufficient energy to react, increasing the rate of reaction without being consumed in the process.</p>
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Explain why alkenes undergo addition reactions, while alkanes typically undergo substitution reactions.

<p>Alkenes contain a carbon-carbon double bond, which is a region of high electron density that can be easily attacked by electrophiles, leading to addition reactions. Alkanes have only single bonds, which are less reactive and require stronger conditions for substitution reactions.</p>
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Describe the trend in reactivity of halogens as you go down the group, and explain the reason for this trend.

<p>The reactivity of halogens decreases as you go down the group because the atomic radius increases, reducing the attraction of the nucleus for an electron, making it harder to gain an electron and form a negative ion.</p>
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Explain why noble gases are generally unreactive.

<p>Noble gases have a full outer electron shell, making them stable and not prone to gaining, losing, or sharing electrons to form chemical bonds.</p>
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Describe the acid rain creation process, starting from the release of pollutants.

<p>The release of sulfur dioxide and nitrogen oxides into the atmosphere will react with water, oxygen, and other chemicals to form sulfuric and nitric acids. These acids mix with water and fall as acid rain.</p>
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Explain why the rate of reaction decreases over time if the concentration of reactants is not maintained.

<p>As the reaction proceeds, the concentration of reactants decreases, resulting in fewer collisions between reactant particles, decreasing the rate of successful collisions, hence, the rate of reaction decreases.</p>
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Describe the difference between empirical and molecular formulas.

<p>An empirical formula shows the simplest whole number ratio of atoms in a compound, while a molecular formula shows the actual number of atoms of each element in a molecule of the compound.</p>
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Explain what is meant by the term 'dynamic equilibrium'.

<p>Dynamic equilibrium is when the rate of the forward reaction equals the rate of the reverse reaction in a closed system, so the concentrations of reactants and products remain constant.</p>
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When considering the collision theory, what are the two requirements for a collision to be successful?

<p>The colliding particles must have energy equal to or greater than the activation energy, and the particles must have proper orientation.</p>
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Explain how Le Chatelier's principle helps predict the shift in equilibrium when conditions change.

<p>Le Chatelier's principle states that if a change of condition (e.g., temperature, pressure, or concentration) is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.</p>
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Flashcards

What are isotopes?

Elements with the same number of protons but different numbers of neutrons.

What is a saturated solution?

A solution containing the maximum amount of solute capable of dissolving at a given temperature.

What is neutralization?

A reaction where an acid and a base react to form a salt and water.

What is Malleability?

The ability to be hammered or pressed permanently out of shape without breaking or cracking.

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Limewater test for CO2

Calcium hydroxide reacts with carbon dioxide to form calcium carbonate and water.

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What is a Homologous Series?

A series of organic compounds with the same functional group and similar chemical properties.

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What is a condensation polymer?

A polymer formed by joining monomers, with the removal of small molecules, such as water.

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Study Notes

  • The symbols of the elements of Period 3 of the Periodic Table include, Na, Mg, Al, Si P S Cl and Ar

Question 1a-h

  • Mg forms a stable ion with a 2+ charge
  • Ar is the least reactive element in the period
  • Cl is used in water treatment
  • Si forms an oxide which is the main impurity in iron ore
  • P is an important component of fertilisers
  • Na is stored under oil
  • Al is used in food containers
  • S is found in the ore zinc blende

Question 2a

  • Calcium hydroxide is slightly soluble in water and can be made by reacting calcium with water
  • The chemical equation for the reaction is Ca + 2H2O -> Ca(OH)2 + H2
  • Another substance that reacts with water to form calcium hydroxide is calcium oxide (CaO)

Question 2b

  • Calcium hydroxide dissolves in water, dissociating into ions and forms a weakly alkaline solution
  • The pH of aqueous calcium hydroxide is greater than 7 and less than 14
  • The formula of the ion responsible for the alkaline solution is OH-

Question 2c

  • Limewater is a saturated solution of calcium hydroxide, Ca(OH)2(aq)
  • Limewater tests for carbon dioxide.
  • The term 'saturated solution' means a solution that contains the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature
  • Add solid calcium hydroxide to water, stir to dissolve, and filter to remove any undissolved solid, yielding a clear limewater solution
  • Test the presence of calcium ions: Add aqueous sodium hydroxide to limewater and observe a white precipitate forming

Question 2d

  • A 25.0 cm³ sample of limewater is placed in a conical flask and the concentration of Ca(OH)2 determined via titration with dilute hydrochloric acid (HCl)
  • A burette measures the volume of acid in the titration
  • The type of reaction taking place is neutralisation
  • An indicator is added to the conical flask, as well as the limewater and dilute hydrochloric acid
  • The equation for the reaction is Ca(OH)2+ 2HCl -> CaCl2 + 2H2O
  • 20.0 cm³ of 0.0500 mol/dm³ HCl reacts with the 25.0 cm³ of Ca(OH)2

Question 3a

  • Transition elements are in the middle block of the Periodic Table
  • Chromium has several isotopes, while Manganese has only one isotope
  • Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons
  • The nucleon number of manganese is 55

Question 3b

  • One chemical property of transition elements is that they form colored compounds
  • Hydrated copper (II) sulfate is blue
  • Hydrated cobalt (II) chloride is pink
  • Two other chemical properties of transition elements are that they have variable oxidation states and act as catalysts

Question 3c

  • Transition and Group I elements are metals, and both conduct electricity and can be hammered into shape
  • Transition and Group I elements conduct electricity because they have delocalised electrons that can move freely through the structure
  • A material that can be hammered into shape is described as malleable

Question 3d

  • Transition elements and Group I elements differ in physical properties, with transition elements being harder and stronger
  • Two other ways Transition elements differ from Group I elements are in density and melting points
  • Transition elements have higher densities
  • Transition elements have higher melting points

Question 4a

  • Fluorine and chlorine are halogens
  • Fluorine's appearance looks like a pale yellow gas

Question 4b

  • Fluorine reacts with sulfur to form a compound, containing 25.2% sulfur by mass and a relative molecular mass of 254
  • The molecular formula of this compound SF6

Question 4c

  • Nitrogen trichloride (NCl3) is a covalent compound
  • The dot-and-cross diagram would show one N atom surrounded by 3 Cl atoms, with single covalent bonds between the N and each Cl
  • There should be a total of 28 outer electrons in the diagram

Question 4d

  • Lithium chloride (LiCl) is an ionic compound
  • The dot-and-cross diagram shows Li with no outer shell electrons and a +1 charge, and Cl with 8 outer shell electrons and a -1 charge

Question 4e

  • LiCl is a solid due to strong attraction forces between particles
  • NCl3 is a liquid with a relatively low boiling point

Question 5a

  • The reaction scheme shows five organic reactions, numbered 1 to 5
  • Reaction 1 is fermentation

Question 5b

  • Reaction 2 is combustion
  • A chemical equation is C2H5OH + 3O2 -> 2CO2 + 3H2O

Question 5c

  • Reaction 3 forms ethanol from alkene A
  • Alkene A is ethene
  • The reaction occurring during reaction 3 is hydration
  • The reagents and conditions needed for reaction 3 are steam and a phosphoric acid catalyst

Question 5d

  • Alkene A (ethene) converts into alkane B in reaction 4
  • The reagent and conditions for reaction 4 are hydrogen and a nickel catalyst
  • The general formula of alkanes is CnH2n+2

Question 5e

  • Ethanol is oxidised in recation 5, heated with dilute sulfuric acid and one other reagent
  • The other reagent in reaction 5 is potassium dichromate
  • Compound C belongs to the carboxylic acids homologous series
  • The structure of compound C is ethanoic acid

Question 6a

  • Polymer X is a condensation polymer
  • Two molecules of water are produced when this part of polymer X is formed from its monomers

Question 6b

  • Polymer Y's structure is available
  • Two different types of monomer are needed to make polymer Y.

Question 6c

  • Polymer Z's structure is available
  • The stucture of the monomer which forms polymer Z is propene
  • The chemical process used to make the monomer that forms polymer Z is cracking

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