Questions and Answers of Cambridge International AS And A Level Chemistry

Write short notes on the following methods of synthesising chiral molecules:a. Using a chiral auxiliaryb. Use of a chiral pool.
The structure of the compound known as thalidomide can be shown as:a. Copy the molecule and mark the chiral centre on your drawing.b. Name two functional groups found in a molecule of thalidomide.c.
The flow charts below show how poly(ethene) can be obtained by two different routes.a. i. Identify substance A and give the equation for the reaction taking place in process 1.ii. What term is used
Diffusion in a gas is the random motion of particles involved in the net movement of a substance from an area of high concentration to an area of low concentration. The process of diffusion also
a. Name the organic products A to D in the synthetic route below:b. i. Devise a three-stage synthetic route to convert benzene into benzenediazonium chloride.ii. How would you convert the
a. Describe in general terms what is meant by desorption.b. Nickel acts as a catalyst for the hydrogenation of alkenes. For example:Suggest how nickel catalyses this reaction by referring to the
a. For this question refer back to Figure 23.3. If there are four molecules in the gas jar on the left, how many ways of arranging the molecules are there when the partition is removed?b. What is the
Graphite and diamond are both forms of carbon. Their standard molar entropies are:ΔSθgraphite = 5.70 J K–1 mol–1, ΔSθdiamond = 2.40 J K–1mol–1a. i. Suggest why the standard molar
Calculate the total standard entropy change in each of the following reactions using the standard molar entropy values given here.(Values for Sθin J K–1 mol–1: C(graphite) = 5.700,C2N2(g) =
a. For each of the following pairs of compounds, state with reasons which one you would expect to have the higher lattice energy.i. NaCl and KBrii. KCl and SrS.b. In some crystal lattices, some of
a. Write equations to represent the enthalpy change of solution of:i. Potassium sulfateii. Zinc chloride.b. The enthalpies of solution of some metal halides are given below. What do these values tell
An accurate value of the Faraday constant is 96,485 C mol–1. An accurate value for the charge on one electron is 1.6022 × 10–19 C. Use these values to calculate a value of the Avogadro constant
Compare and comment on your answers to questions 32 and 33.Data from question no.32A car’s fuel tank holds 40 kg of petrol.■■ 1 kg of petrol releases 5 × 107 J of energy when it burns.■■
The rate of reaction between butanone and iodine is studied. In this experiment, iodine is in excess. The concentration of butanone is measured at various time intervals. The results are shown in the
Convert the following rates into the units of mol dm–3 s–1:a. 0.254 g of I2 consumed in 1.00 h in a reaction mixture of volume 1 dm3 (Ar[I] = 127)b. 0.0440 g ethyl ethanoate formed in 1.00
The reactionA + B + C → ABCis zero order with respect to one reactant, first order with respect to another reactant and second order with respect to another reactant.a. i. Explain what is meant by
a. Suggest a suitable method for following the progress of each of these reactions:i. H2O2(aq) + 2I–(aq) + 2H+(aq) → 2H2O(l) + I2(aq)ii. HCOOCH3(aq) + H2O(l) → HCOOH(aq) + CH3OH(aq)iii.
i. Plot the data in Table 22.1 for increase in propene concentration with time.ii. Calculate the rate after 10 minutes (when the propene concentration is 0.50 mol dm–3) by drawing a tangent.b. Use
The rate equation for the reaction between iodine and propanone is:rate = k[CH3COCH3] [H+] [I2]0a. State the order of reaction with respect to iodine.b. State the overall order of reaction.c. i. What
The decomposition of hydrogen peroxide, H2O2, to oxygen and water is catalysed by manganese(IV) oxide.a. Define the term catalyst.b. The results for the decomposition of a sample of hydrogen peroxide
Write rate equations for each of the following reactions:a. Cyclopropane → propene where rate is proportional to the concentration of cyclopropaneb. 2HI(g) → H2(g) + I2(g) where rate is
Peroxodisulfate ions, S2O82–, react with iodide ions in aqueous solution to form iodine and sulfate ions.S2O82–(aq) + 2I–(aq) → 2SO42–(aq) + I2(aq)
For each of the reactions a to e in question 4, state:i. The order of reaction with respect to each reactantii. The overall order of reaction.
The rate of reaction between butanone and iodine is studied. In this experiment, butanone is in excess. The concentration of iodine is measured every 10 minutes for 1 hour. The results are shown in
For each of the reactions a to c in question 7, draw a sketch graph to show how the concentration of the bold reactant changes with time.Data from question 7Draw sketch graphs of reaction rate
State the units of k corresponding to each of the following rate equations:a. Rate = k[NO]2b. Rate = k[NH3]0c. Rate = k[BrO3–] [Br–][H+]2d. Rate = k[cyclopropane]
Nitrogen oxides can be removed from the exhaust gases of a car engine by using a catalytic converter. Many catalytic converters contain metals such as platinum and rhodium. These act as heterogeneous
Bromate(V) ions react with bromide ions in acidic solution to form bromine.BrO3–(aq) + 5Br –(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(l)a. Suggest two methods of following the progress of this
Benzenediazonium chloride, C6H5N2Cl, decomposes at room temperature:C6H5N2Cl(aq) + H2O(l) → C6H5OH(aq) + N2(g) + HCl(aq)a. Describe how this reaction can be monitored.b. Using the data in the
Suggest how the experiment for the reaction between methanol and hydrochloric acid might be re-designed to obtain evidence for the effect of changing the HCl concentration whilst controlling the
a. State the order of reaction for the decomposition of nitrogen(V) oxide.b. Use the data for 3.00 mol dm–3 N2O5 in Table 22.8 to calculate a value for the rate constant for this decomposition.
a. Write the rate equation for the acid-catalysed reaction of iodine with propanone.b. Use your rate equation and the information in Table 22.9 (experiment 1) to calculate a value for the rate
An acidified solution of hydrogen peroxide reacts with iodide ions.H2O2(aq) + 2H+(aq) + 2I–(aq) → 2H2O(l) + I2(aq)The rate equation for this reaction is rate = [H2O2] [I–] The mechanism below
a. State which pairs of substances i to iv below might catalyse the reaction:S2O82–(aq) + 2I–(aq) → 2SO42–(aq) + I2(aq)Explain your answer.i. Ni2+(aq) / Ni(s)
Explain the difference in the entropy of each of the following pairs of substances in terms of their state and structure. a Br, (1) S° = 151.6JK mol1 and I,(s) S° = 116.8 JK'mol-1 b H,(g) Se =
For each of the following reactions, suggest whether the entropy of the reactants or the products will be greater or whether it is difficult to decide. Explain your answers.a. NH3(g) + HCl(g) →
At 10 °C ice changes to water.H2O(s) → H2O(l)
Calculate the standard entropy change of the system in each of the following reactions using the standard molar entropy values given here.(Values for Sθin J K–1 mol–1: Cl2(g) = 165.0,Fe(s) =
Barium carbonate decomposes when heated.BaCO3(s) → BaO(s) + CO2(g)a. Use your knowledge of Hess cycles from Chapter 6 to calculate the enthalpy change of this reaction. Express your answer to three
Calculate the entropy change of the surroundings in each of the following reactions. Assume that the value of ΔH does not change with temperature.a. C(s) + O2(g) → CO2(g)
a. For each of the following changes state whether the entropy of the system decreases or increases. In each case, explain your answer in terms of the order or disorder of the particlesi. NaCl(s) +
a. i. Define standard free energy change of formation.ii. Write a balanced equation to represent the standard free energy change of formation of ethane. Include state symbols in your answer.b. The
The decomposition of calcium carbonate, CaCO3(s) → CaO(s) + CO2(g), does not take place at room temperature.a. Explain in terms of entropy changes why heating the calcium carbonate to a high
Calcium carbonate decomposes when heated to form calcium oxide and carbon dioxide.CaCO3(s) → CaO(s) + CO2(g)a. Calculate the entropy change of the system for this reaction.(Values for Sθin J
Water is formed when hydrogen burns in oxygen.2H2(g) + O2(g) → 2H2O(l) ΔHθr = –561.6 kJ–1 mol–1a. Calculate the entropy change of the system for this reaction.(Values for Sθin J K–1
Calculate the standard Gibbs free energy of reaction in each of the following using the standard molar entropy values given. Express your answers to 3 significant figures in kJmol1, and in each case
Calculate the standard Gibbs free energy change of reaction in each of the following using the standard molar values for Gibbs free energy change given here. In each case, comment on whether the
a. Suggest a suitable indicator to find the end-points of the reactions between:i. 0.0500 mol dm–3 nitric acid and 0.0500 mol dm–3 aqueous ammoniaii. 2.00 mol dm–3 aqueous sodium hydroxide and
a. Draw an enthalpy cycle to calculate the enthalpy of hydration of magnesium ions when magnesium chloride dissolves in water.b. Calculate the enthalpy of hydration of magnesium ions given
a. Draw an enthalpy cycle as an energy level diagram showing the relationship between lattice energy, enthalpy change of solution and enthalpy change of hydration for barium sulfate.ΔHQsol[BaSO4] is
Calculate the volume of oxygen produced at r.t.p. when a concentrated aqueous solution of sodium sulfate is electrolysed for 55.0 min using a current of 0.70 A.(F = 96 500 C mol–1; 1 mole of gas
Refer to the list of electrode potentials below to answer parts a to d.Ag+(aq) + e– ⇌ Ag(s) voltage = +0.80 V Co2+(aq) + 2e– ⇌ Co(s) voltage = –0.28 VCu2+(aq) +
A solution of butanedioic acid (BDA) in ether contains 0.034 mol of BDA in 20 cm3 of ether. This solution is shaken with 50 cm3 of water. The mass of BDA extracted into the water layer after shaking
a. Thallium(I) chloride is a salt that is sparingly soluble in water. When hydrochloric acid is added to a saturated solution of thallium(I) chloride, a precipitate is formed. Explain why a
a. Calculate the solubility product of the following solutions:i. A saturated aqueous solution of cadmium sulfide, CdS (solubility = 1.46 × 10–11 mol dm–3)ii. A saturated aqueous solution of
a. Write equilibrium expressions for the solubility products of the following:i. Fe(OH)2ii. Fe2S3iii. Al(OH)3b. State the units of solubility product for each of the compounds in part a.
a. One of the buffers in blood plasma is a mixture of dihydrogenphosphate ions (H2PO4–) and hydrogenphosphate (HPO42–) ions.i. Identify the conjugate acid and base in this buffer.ii. Write a
a. Calculate the pH of the following buffer solutions:i. 0.0500 mol dm–3 methanoic acid and 0.100 mol dm–3 sodium methanoate. (Ka of methanoic acid = 1.60 × 10–4 mol dm–3)ii. 0.0100 mol
A mixture of 0.500 mol dm–3 aqueous ammonia and 0.500 mol dm–3 ammonium chloride acts as a buffer solution.a. Explain how this buffer solution minimises changes in pH on addition ofi. Dilute
a. What is the pH of 0.25 mol dm–3HCl(aq)?b. What is the pH of 0.0500 mol dm–3 sodium hydroxide? (Kw = 1.00 × 10–14 mol2 dm–6)c. The graph shows how the pH changes when 0.100 mol dm–3
Use Table 21.3 to identify:a. Those indicators which could be used for a strong acid–strong base titration like the one in Figure 21.8.b. Those indicators that could not be used. Name of dye Colour
A saturated solution of copper(I) sulfide, Cu2S, contains 1.91 × 10–12 g of Cu2S dissolved in 1 dm3 of water. (Ar values: Cu = 63.5, S = 32.1)a. Write an equilibrium expression for the solubility
Use the data from Table 21.2 to work out the pH values of the following solutions:a. 0.0200 mol dm–3 aqueous benzoic acidb. 0.0100 mol dm–3 hydrated aluminium ionsc. 0.100 mol dm–3 aqueous
A buffer solution consists of 6.00 g of ethanoic acid (CH3COOH) and 12.3 g of sodium ethanoate (CH3COONa) in 200 cm3 of aqueous solution.(Ar values: H = 1.0, C = 12.0, O = 16.0, Na = 23.0; Ka for
a. Calculate the value of Ka for the following acids:i. 0.0200 mol dm–3 2-aminobenzoic acid, which has a pH of 4.30ii. 0.0500 mol dm–3 propanoic acid, which has a pH of 3.10iii. 0.100 mol dm–3
Copper(I) bromide, CuBr, is a sparingly soluble salt. (Ksp = 3.2 × 10–8 mol2 dm–6)a. What do you understand by the terms:i. Solubility productii. Common ion effectb. Calculate the solubility of
a. Write equilibrium expressions for the following reactions:i. C6H5COOH(aq) ⇌ H+ (aq) + C6H5COO–(aq)ii. HCO3–(aq) ⇌ H+(aq) + CO32–(aq) iii. NH4+(aq) ⇌ H+(aq) + NH3(aq)b.
a. What is the pH of a solution containing 0.100 mol dm–3 ethanoic acid and 0.100 mol dm–3 sodium ethanoate? (Ka of CH3COOH = 1.74 × 10–5 mol dm–3)b. How many moles of sodium ethanoate
Find the pH of the following strong acids and strong bases:a. 1.00 mol dm–3 HNO3b. 0.500 mol dm–3 HNO3c. An aqueous solution containing 3.00 g HCl per dm3d. 0.001 00 mol dm–3 KOH (Kw =
a. Sketch the graph of pH that would be obtained when 10.0 cm3 of 0.200 mol dm–3 HCl is titrated against 0.200 mol dm–3 aqueous ammonia.b. Explain why methyl orange is a suitable indicator for
Calculate the concentration of hydrogen ions in solutions having the following pH values:a. pH 2.90 b. pH 3.70 c. pH 11.2d. pH 5.40 e. pH 12.9
a. Write general expressions for the terms:i. pHii. Kwiii. Kab. What is the pH of 0.004 00 mol dm–3 HCl(aq)? Show your working.c. What is the pH of 0.004 00 mol dm–3 butanoic acid(aq)? (Ka = 1.51
Calculate the pH of the following solutions:a. [H+] = 3.00 × 10–4 mol dm–3b. [H+] = 1.00 × 10–2 mol dm–3c. [H+] = 4.00 × 10–8 mol dm–3d. [H+] = 5.40 × 10–12 mol dm–3e. [H+] = 7.80
A concentrated aqueous solution of hydrochloric acid is electrolysed.a. Write half-equations to show the reactions at:i. The cathodeii. The anode.b. A very dilute solution of hydrochloric acid is
Predict the electrolysis products at the anode and cathode when the following are electrolysed:a. Molten aluminium iodideb. A concentrated aqueous solution of magnesium chloridec. A concentrated
An aqueous solution of sodium sulfate, Na2SO4, is electrolysed using carbon electrodes.a. Explain why hydrogen is formed at the cathode and not sodium.b. Write a half-equation for the reaction
A fuel cell vehicle with a similar volume fuel tank can store 400 g of hydrogen at high pressure.■ 2 g of hydrogen release 286 000 J of energy when used in the vehicle’s fuel cells.■ 60% of the
A car’s fuel tank holds 40 kg of petrol.■ 1 kg of petrol releases 5 × 107 J of energy when it burns.■ Only 40% of the energy released when the petrol burns is converted into useful work.■ 1
Lithium is often used as the negative pole in ‘button’ cells used to power watches.a. Explain why lithium is often used to make electrochemical cells.b. The half-equations for a lithium/iodine
The nickel–cadmium cell is rechargeable. The half equations for the electrode reactions are:Cd(OH)2 + 2e– → Cd + 2OH–
Describe two limitations to using Eθ values to predict the feasibility of a reaction.
An industrial process relies on a reaction that is impractically slow under normal conditions. How might you try to solve this problem? Use your knowledge of reaction rates to suggest several
a. Calculate the value of the electrode potential at 298 K of a Ni(s)/Ni2+(aq) electrode that has a concentration of Ni2+(aq) ions of 1.5 mol dm–3.Eθ= –0.25 V.b. Calculate the electrode
The half-cell Cr2O7 2– + 14H+ + 6e– ⇌ 2Cr3+ + 7H2O has an Eθ value of +1.33 V.a. Suggest how the value of Eθchanges if the other species are kept at 1.00 mol dm–3 but:i.
Use the Eθ values for the halogens to explain the following:a. Why bromine can oxidise an aqueous solution of Iodide ions.b. Why bromine does not react with chloride ions.
Use the data in Appendix 2 to answer these questions.a. Of the ions Ag+, Cr2+ and Fe2+, which one needs the strongest reducing agent to reduce it to metal atoms?b. Of the atoms Ag, Cr and
The reaction taking place in an electrochemical cell under standard conditions is Fe2+(aq) + Ag+(aq) Fe3+(aq) + Ag(s)a. Write two half-equations for this reaction. For each, state whether oxidation
Liquid bromine is added to an aqueous solution of potassium iodide. The following reaction takes place.Br2(l) + 2I–(aq) 2Br –(aq) + I2(aq) Eθcell = +0.53 Va. Write two half-equations for this
a. Define the term standard electrode potential.b. Draw a labelled diagram to show how the standard electrode potential of a half-cell containing chlorine gas and chloride ions can be measured.c.
In each of the chemical reactions a to c:i. Which species gains electrons?ii. Which species loses electrons?iii. Which species is the oxidising agent?iv. Which species is the reducing agent?a. CuCl2
se the cell voltage method described in Worked examples 6 and 7 above to answer question 21, parts a to d.Data From Question 21:Use the data in Appendix 2 (page 474) to predict whether or not the
Suggest a suitable reagent that can carry out each of the following oxidations or reductions. Use the data in Appendix 2 to help you.a. The reduction of Zn2+ ions to Zn.b. The oxidation of
Use the data in Appendix 2 to predict whether or not the following reactions are feasible. If a reaction does occur, write a balanced equation for it.a. Can MnO4 – ions oxidise Cl– ions to
State the direction of the electron flow in the electrochemical cells represented by the following pairs of half-equations. Use the data in Appendix 2 to help you.a. F2 + 2e– ⇌ 2F– and
a. Draw a diagram of an electrochemical cell consisting of a Mn2+/Mn half-cell and a Pb2+/Pb half-cell.b. Use the data in Appendix 2 to calculate the cell voltage.c. Which half-cell is the
a. Draw a diagram of an electrochemical cell consisting of a Cr3+/Cr half-cell and a Cl2/Cl– half-cell.b. Use the data in Appendix 2 to calculate the cell voltage.c. Which half-cell is the positive
Show, with the aid of a diagram, how you would measure the EQ value for the half-cell shown by the equation:VO2+ + 2H+ + e– ⇌ V3+ + H2O
Why is platinum used in preference to other metals in half-cells where the reaction does not involve a metallic element?
What is the Eθvalue for the half-cell on the left-hand side of Figure 20.14? 1.52 V voltmeter - H,(g). 1 atmosphere platinum salt bridge - platinum 298 K H*, 1.00 mol dm-3 MnO, 1.00 mol dm Mn2",
Draw a diagram to show how you would measure the standard electrode potential for the half-cell:1/2 I2 + ⇌ e– I–(aq)Include the actual Eθ value of +0.54 V on your diagram.

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