Questions and Answers of Cambridge International AS And A Level Chemistry

a. Look at Figure 20.12. Write a half-equation for the half-cell on the left-hand side.b. What is theEθvalue for this half-cell? 0.51 V voltmeter -H,(8), 1 atmosphere platinum salt bridge - platinum
a. Write half-equations for the three reactions taking place in the half-cells shown on the left in Figure 20.10.b. What are the standard electrode potentials for these half-cell reactions?c. List
a. Suggest why aqueous silver nitrate is not used in a salt bridge when connecting a half-cell containing Zn and 1.00 mol dm–3 ZnCl2(aq) to another half-cell.b. Write half-equations for the
Concentrated aqueous sodium chloride can be electrolysed in the laboratory using graphite electrodes.a. Write the formulae for all the ions present in an aqueous solution of sodium chloride.b. Write
An aqueous solution of silver nitrate is electrolysed.a. i. Explain why silver rather than hydrogen is produced at the cathode.ii. Write an equation for the reaction occurring at the cathode.b. i.
A student passed a constant electric current of 0.15 AV through a solution of silver nitrate, using pure silver electrodes, for 45 min exactly. The mass of the anode decreased by 0.45 g. Use this
An electric current of 1.04 A was passed through a solution of dilute sulfuric acid for 6.00 min. The volume of hydrogen produced at r.t.p. was 43.5 cm3.a. How many coulombs of charge were passed
The list below gives the standard electrode potentials for five half-reactions.Cu2+(aq) + e– Cu(s) Eθ= +0.34 VFe2+(aq) +
Calculate the volume of hydrogen produced at r.t.p. when a concentrated aqueous solution of sulfuric acid is electrolysed for 15.0 min using a current of 1.40 A.(F = 96 500 C mol–1; 1 mole of gas
Calculate the mass of silver deposited at the cathode during electrolysis when a current of 1.80 A flows through an aqueous solution of silver nitrate for 45.0 min.(Ar value: [Ag] = 108; F = 96 500 C
a. In the presence of acid, the manganate(VII) ion is a powerful oxidising agent. The half-equation for its reduction in acid solution is:MnO4–(aq) + 8H+(aq) + 5e– ⇌ Mn2+(aq) + 4H2O(l)
a. Explain why cations move towards the cathode during electrolysis.b. When lead iodide, PbI2, is electrolysed the following reactions occur:Pb2+ + 2e– → Pb and 2I– → I2 + 2e–i. Which of
a. Why does an ionic compound have to be molten to undergo electrolysis?b. Give two properties of graphite that make it a suitable material for use as an electrode. Explain your answers.
The diagram shows an electrochemical cell involving two metal/metal-ion systems.The standard electrode potentials for the half-cells are:Ag+ + e– ⇌ Ag
Construct full redox equations from the following pairs of half-equations.a. The reaction of iodide ions with hydrogen peroxide:I– → 1/2 I2 + e–H2O2 + 2H+ + 2e– → 2H2Ob. The reaction of
The diagram shows an electrochemical cell designed to find the standard electrode potential for zinc.a. Name the apparatus labelled a and give a characteristic it should have.b. i. Name part b and
Name the changes associated with the equations below:a. KBr(s) + aq → KBr(aq) (for 1 mole of KBr)b. K+(g) + aq → K+(aq) (for 1 mole of K+ ions)c. K+(g) + Br–(g) → KBr(s) (for 1 mole of KBr)d.
a. Why is the enthalpy change of hydration always exothermic?b. Write equations to represent:i. The hydration of a sodium ionii. The hydration of a chloride ion.c. Draw diagrams to show:i. 4 water
a. Explain why a cation with a smaller ionic radius has a higher charge density.b. Which one of the following ions will be the best polariser of the large nitrate ion? Explain your answer.Cs+ Li+ N
Use ideas about ion polarisation to explain why magnesium nitrate undergoes thermal decomposition at a much lower temperature than barium nitrate.
Students taking physics A level learn that the electrostatic force between two charged particles is proportional towhere Q1 and Q2 are the charges on the particlesand r is the distance between the
a. For each pair of compounds, suggest which will have the most exothermic lattice energy.i. KCl and BaO (ionic radii are similar)ii MgI2 and SrI2iii CaO and NaCl (ionic radii are similar).b. Place
a. Draw a Born–Haber cycle for aluminium oxide.b. Calculate a value for the lattice energy of aluminium oxide using the data under the arrows in the sequences above and given that ΔHQf[Al2O3] =
The diagram shows the enthalpy changes when sodium chloride is dissolved in water.a. Define the following terms:i. Enthalpy change of solutionii. Enthalpy change of hydration.b. Write symbol
Draw fully labelled Born–Haber cycles for:a. MgOb. Na2O.
a. Draw a fully labelled Born–Haber cycle for potassium bromide, naming each step.b. State the name of the enthalpy changes represented by the following equations:i. I2(s) → I(g)ii. N(g) + e–
The lattice energy of magnesium bromide, MgBr2, can be calculated using the enthalpy changes shown in the table.a. State the meaning of the terms:i. Lattice energyii. 2nd ionisation energy.b. Draw
a. Write equations to represent:i. The 1st ionisation energy of caesiumii. The 3rd ionisation energy of aluminiumiii. The enthalpy change of formation of calcium oxideiv. The enthalpy change of
You have to identify an unknown compound, x.a. From the results of the tests above, and the Tables of Qualitative Analysis, identify the cation present in x.b. Suggest another reagent to confirm the
a. Draw an enthalpy (Hess’s law) cycle to show the dissolving of magnesium iodide in water.b. The table shows the values for all but one of the enthalpy changes relevant to this cycle.i. Define
a. Suggest why the 2nd and 3rd electron affinities are always endothermic.b. The 1st electron affinity of sulfur is –200 kJ mol–1. The second electron affinity of sulfur is +640 kJ mol–1.
The rate of the following reaction between hydrogen peroxide (H2O2) and iodide ions can be monitored using sodium thiosulfate and starch indicator:2H+(aq) + H2O2(aq) + 2I–(aq) → 2H2O(l) + I2(aq)A
The lattice energy of sodium chloride can be calculated using the following enthalpy changes:■ Enthalpy change of formation of sodium chloride■ Enthalpy changes of atomisation of sodium and
a. The bond energy of the chlorine molecule is +244 kJ mol–1. Why is the standard enthalpy change of atomisation half this value?b. Write equations, including state symbols, that represent the
A student investigated the ease with which various metal carbonates decompose on heating. She decide to heat equal masses of each carbonate and time how long it took for the carbon dioxide
The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, K2O.a. Copy the incomplete Born–Haber cycle shown below. On the lines A to E of your copy of the
a. Give values for the standard conditions of temperature and pressure.b. Write equations describing the lattice energy of:i. Magnesium oxideii. Potassium bromideiii. Sodium sulfide.
a. How would you make ethanoic acid from ethanenitrile?b. Write a balanced equation, using structural formulae for the organic compounds, to show the formation of:i. Sodium methanoate, using sodium
Bromine can react with ethane to form bromoethane.a. What conditions are needed for the reaction between ethane and bromine to take place?b. What do we call this type of reaction?c. Write an equation
a. The pH of a solution depends on the hydrogen ion (hydroxonium ion) concentration. Which concentration of ethanoic acid in Table 8.8 has the highest concentration of hydrogen ions in solution?b.
Calculate the value of Kc for the following reaction using the information below:H2(g) + CO2(g) ⇋ H2O(g) + CO(g)Initial concentration of H2(g) = 10.00 mol dm–3.Initial concentration of
The compound KBrO3 decomposes when heated.2KBrO3 → 2KBr + 3O2a. State the oxidation numbers of bromine in:i. KBrO3 ii. KBr.b. Explain using oxidation numbers why this reaction is a redox
a. Write two half-equations for the following reactions. For each half-equation state whether oxidation or reduction is occurring.i. Cl2 + 2I– → I2 + 2Cl–ii. 2Mg + O2 → 2MgOiii. 4Fe + 3O2 →
a. In each of the following equations, state which reactant has been oxidised:i. PbO + H2 → Pb + H2Oii. CO + Ag2O → 2Ag + CO2iii. 2Mg + CO2 → 2MgO + Cb. In each of the following equations,
The equation for the combustion of ethanol is:C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)a. Rewrite this equation to show all the bonds in the reactants and products.b. Use the following bond energies
In an experiment, a spirit burner is used to heat 250 cm3 of water by burning methanol (CH3OH). (Ar values: C = 12.0, H = 1.0, O = 16.0; specific heat capacity of water = 4.18 J
a. Define enthalpy change of solution.b. Given the enthalpy changes ΔH1 and ΔH2 below, construct a Hess’s cycle that will enable you to find the enthalpy change, ΔHr, for the reaction:MgCl2(s) +
Copper(II) nitrate decomposes on heating. The reaction is endothermic.2Cu(NO3)2(s) → 2CuO(s) + 4NO2(g) + O2(g)a. Draw an enthalpy level diagram (reaction profile diagram) for this reaction.b. Draw
Use data from the table below of characteristic infra-red absorptions in organic molecules to answer the following question.One of the three spectra labelled A to c below is produced when ethanal is
Look at the two infra-red spectra below:a. Which one of the infra-red spectra is that of butanone and which one is of butan-2-ol?b. Explain your reasoning in part a. В 20 20- 40 40- 60 60 80 08 100
An alcohol has the molecular formula C3H8O. When warmed with an alkaline solution of iodine it forms a yellow precipitate.a. Name the yellow precipitate.b. Draw the displayed formula of the
a. i. When propanone is warmed with alkaline iodine solution, a yellow precipitate is formed. Name and draw the displayed formula of the yellow precipitate.ii. Give the structural formulae of the
A compound, X, has the following percentage composition: 66.7% carbon, 11.1% hydrogen and 22.2% oxygen.a. Calculate the empirical formula of X.b. The relative molecular mass of X is 72. Calculate the
Ethanol can be made from ethanal using sodium tetrahydridoborate(III) as a reducing agent.a. Give the formula of sodium tetrahydridoborate(III).b. What other reagent is necessary for the reaction to
The melting points of the derivatives of the reaction between 2,4-DNPH and various aldehydes and ketones are shown in the table.a. What would be observed when each of the carbonyl compounds in the
a. Name the organic product that would be formed in the nucleophilic addition of HCN to:i. Ethanalii. Propanone.b. Use diagrams and curly arrows to describe the mechanism of the reaction in part a i.
a Draw the skeletal formulae of:i. Pentan-2-oneii. Pentan-3-oneiii. Pentanal.b. Describe the results you would expect to see if pentan-3-one and pentanal were separately treated with Tollens’
a. Write a balanced equation for the reaction that takes place when propanal is warmed with an aqueous alkaline solution of sodium tetrahydridoborate, using the symbol [H] to represent a hydrogen
a. What reagent would you add to an unknown compound to see if it contains a carbonyl group?b. What result would you get if the unknown compound did contain a carbonyl group?c. Why would it be useful
a. i. Write a balanced equation for the oxidation of ethanol to ethanal, using [O] to represent an oxygen atom from the oxidising agent.ii. Give practical details to explain how you would use the
a. Name the following compounds:i. CH3COCH3ii. CH3CH2CH2OHiii. CH3CHOiv. CH3CH(OH)CH3v. CH3COCH2CH3vi. CH3CH2CHOb. Which of the compounds in part a are alcohols and which are carbonyl compounds?c.
a. Name the following compounds:i. CH3CH2CH2CH2CH2CHOii. CH3CH2CH2CH2CH2CH2COCH3b. Draw the displayed formula of:i. Methanalii. Propanaliii. Pentan-3-one.c. Draw the skeletal formula of the compounds
Propan-1-ol can be oxidised to propanal, CH3CH2CHO, and then to propanoic acid, CH3CH2COOH.a. What reagents and conditions should be used to oxidise propan-1-ol to propanal?b. Write a balanced
Concentrated sulfuric acid or phosphoric acid can also be used to catalyse the dehydration of an alcohol. The alcohol and concentrated acid are heated to about 170°C. The concentrated acid does not
a. Name the ester formed in each of the following reactions:i. Butan-1-ol + ethanoic acidii. Ethanol + hexanoic acidiii. Pentan-1-ol and methanoic acid.b. Write the structural formula of each ester
Lithium reacts with alcohols in a similar way to sodium. A small piece of lithium metal is dropped onto a watch-glass containing propan-1-ol.a. What would you observe?b. Name the products of the
Primary and secondary alcohols can be oxidised by heating with a mixture of potassium dichromate(VI) and dilute sulfuric(VI) acid.A primary alcohol can be oxidised to two different products,
a. Write a balanced equation to show the reaction between ethanol and hydrogen bromide.b. What are the reagents and conditions used for this reaction?c. What do we call this type of reaction?
Write a balanced chemical equation for each of the following processes. Structural or displayed formulae should be used for all organic substances.a. Making ethanol using ethene as feedstock. Include
a Write a balanced equation for the complete combustion of:i. Propan-1-olii. Butan-1-ol.b. Glucose can be fermented with yeast in anaerobic conditions. Name the products of the reaction.
Pentan-2-ol, butan-1-ol and 2-methylpropan-2-ol are alcohols.a. For each one:i. Give its molecular formulaii. Give its structural formulaiii. Give its displayed formulaiv. Give its skeletal formulav.
a. Explain how hydrogen bonds arise:i. Between ethanol moleculesii. Between ethanol and water molecules.b. Ethanol mixes with water in all proportions but hexan-1-ol is less miscible with water. Why
Write a balanced equation for the reaction of bromoethane with ethanolic sodium hydroxide.
How can such unreactive compounds as CFCs cause so much damage to the ozone layer?
a. Draw the structure (displayed formula) of 2-chloro-2-methylbutane.b. Show the mechanism for the hydrolysis of 2-chloro-2-methylbutane by alkali.
Show the mechanism, including appropriate curly arrows, for the hydrolysis of 1- chloropropane, CH3CH2CH2Cl, by alkali.
Bromochlorodifluoromethane has been used in fire extinguishers. However, its breakdown products were found to be toxic.a. Draw the displayed formula of bromochlorodifluoromethane.b. CF3CH2F is being
a. Why can ammonia and amine molecules act as nucleophiles?b. When ammonia is reacted with an excess of a halogenoalkane, a mixture of amines can be formed. If we start with an excess of
1-bromobutane will undergo reactions when heated, as shown by reactions A and B.a. For reactions A and B give the reagents used in each case.b. Reaction A was repeated using 1-iodobutane instead of
a. Why does the hydrolysis of a halogenoalkane happen more quickly with OH–(aq) ions than with water molecules?b. Explain why silver nitrate solution can be used to investigate the rate of
Name the monomer used to make this polymer: GHs H C,Hs H C,Hs H -с —с —с—с—с — с- H H H H H H
a. How could poly(alkene) waste be used to conserve fossil fuels?b. Why would your answer to part a add to the problem of enhanced global warming?c. A waste batch of poly(ethene) pellets was burnt in
Tetrafluoroethene, C2F4, is the monomer for the polymer PTFE, which is used in the non-stick coating on pans.a. What does PTFE stand for?b. What do we call the type of reaction used to form PTFE?c.
a. i. What effect does a hot, concentrated solution of acidified potassium manganate(VII) have on an alkene?ii. Why is this reaction useful to chemists?b. An alkene is known to be either but-1-ene or
a. Name and draw the displayed formula of the organic product formed when propene is oxidised by a cold solution of acidified potassium manganate(VII).b. Name and draw the displayed formula of the
Alkenes are important industrial chemicals, particularly as raw materials for the manufacture of polymers. Ethene can be used to make poly(ethene). Ethene is used to make chloroethene, which is then
Draw the displayed formula of:a. Propylbenzeneb. 1-ethyl-4-methylbenzenec. 1,3,5-triethylbenzene, using the skeletal formula of benzene in the formulae as shown in Figure 14.11. H H H H H displayed
a. Draw the displayed formula of:i. 2-methylbutaneii. 3,5-diethylheptaneiii. 2,4,6-trimethyloctane.b. What is the name of the following hydrocarbon? CH3 CH;CH,CCH,CH,CH,CH; 1. CH,CH;
a. Define the term electrophile.b. Explain how a chlorine molecule can act as an electrophile in its reaction with an alkene.c. Draw the mechanism for the reaction between ethene and chlorine.
In a similar reaction to the reaction described in question 8, 2.80g of ethene react with chlorine. 8.91 g of dichloroethane are formed. (Ar values: H = 1.0, C = 12.0, Cl = 35.5) Calculate:a. The
a. State the conditions used in the reaction between an alkene and hydrogen.b. Name the product formed when propene reacts with chlorine.c. Ethanol can be used as a solvent. How is this ethanol made
Use the passage below and your own knowledge to answer the questions that follow. Ethene reacts with bromine to give 1,2-dibromoethane as the only product. The mechanism for the reaction is
a. Alkenes are unsaturated hydrocarbons. Explain the word unsaturated.b. Describe the bonding between the two carbon atoms in ethene.c. Describe and draw the shape of an ethene molecule, labelling
a. Name the first member of the homologous series of alkenes.b. What is the molecular formula of the alkene containing 18 carbon atoms and one C = C bond?c. Look at the equation for cracking given in
Using structural formulae throughout, give balanced symbol equations for the following reactions.a. Propene with bromine.b. Propene with hydrogen. Name the catalyst used. Which industrial process
Propene, cis-pent-2-ene and trans-pent-2-ene are alkenes.a. For each one give:i. Its molecular formulaii. Its structural formulaiii. Its displayed formulaiv. Its skeletal formula.b. Give the general
a. Name two pollutants from a car engine that are oxidised in a catalytic converter.b. Name a pollutant that is reduced in a catalytic converter.c. Which pollutant from a car engine is not diminished
In a similar reaction to the one in question 3, 1.50 g of ethane reacts with chlorine. 1.29 g of chloroethane is formed. (Ar values: H = 1.0, C = 12.0, Cl = 35.5) Calculate:a. The number of moles of
Give the balanced symbol equations for:a. The complete combustion of heptane, C7H16, giving carbon dioxide and waterb. The incomplete combustion of methane, CH4, giving carbon monoxide and waterc.
Use the passage below and your own knowledge to answer the questions that follow. Methane reacts with bromine to give bromomethane and hydrogen bromide. The mechanism for the reaction is called

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