Chemistry 2020 May/June | Past Paper

Q2(a)

Short Answer 1 mark

Describe and explain how the solubility of the Group 2 sulfates varies down the group.

Q2(b)

Short Answer 1 mark

The trend in the decomposition temperatures of Group 2 peroxides, MO , is similar to that of Group 2 carbonates. Suggest which of barium peroxide, BaO , and calcium peroxide, CaO , will decompose at the lower temperature. Explain your answer.

Q2(c)

Short Answer 1 mark

Magnesium iodate( V), Mg(IO , decomposes when heated to form magnesium oxide, oxygen and iodine. Construct an equation for this reaction.

Q2(d)

Short Answer 1 mark

Calcium iodate( V), Ca(IO , is sparingly soluble in water. The concentration of its saturated solution is 5.6 × 10

Q2(i)

Short Answer 2 marks

Write an expression for the solubility product, K , of Ca(IO , and state its units. units =

Q2(ii)

Short Answer 1 mark

Calculate the numerical value for K Ca(IO =

Q2(iii)

Short Answer 1 mark

When a few cm of concentrated Ca(NO

Q2(aq)

Short Answer 1 mark

is added to a saturated solution of Ca(IO a white precipitate forms. Identify the white precipitate and give an explanation for this observation.

Q2(e)

Short Answer 3 marks

Iodised salt is sodium chloride mixed with a small amount of sodium iodate( V), NaIO a volumetric flask with distilled water. of this solution is pipetted into an excess of aqueous acidified potassium iodide. + 5I + 6H + 3H aqueous sodium thiosulfate solution for complete reaction. + 2S + S mass of NaIO = g

Q2(f)

Short Answer 1 mark

The half-equation for the reduction of iodate( V) ions is shown. + 6H + 5e + 3H Use data from the Data Booklet to predict whether a reaction is feasible when aqueous solutions of acidified iodate( V) ions and bromide ions are mixed. Explain your answer.

Q2(g)

Short Answer 1 mark

Iodate( V) ions react with sulfite ions in acidic solution at pH 5.00 as shown. + 3SO + 3SO The initial rate of reaction was found to be first order with respect to IO , first order with respect to SO and first order with respect to H

Q2(i)

Short Answer 2 marks

Write the rate equation for this reaction, stating the units of the rate constant, k. units of k =

Q2(ii)

Short Answer 1 mark

The rate of reaction depends on the pH of the solution. Assume all other concentrations remain the same. Use the expression x = rate at pH 5.00 rate at pH 4.00 to calculate the value of x. x = [1] [Total: 19]

Q3(a)

Short Answer 1 mark

Complete the electronic configuration of an isolated gaseous nickel(II) ion, Ni [Ar]

Q3(b)

Short Answer 1 mark

Explain the origin of colour in transition element complexes.

Q3(c)

Short Answer 1 mark

Hexaaquanickel( II) ions are green. They form a green precipitate with hydroxide ions, OH , in equilibrium 1 and a blue complex with ammonia, NH , in equilibrium 2. equilibrium 1 [Ni(H + 2OH Ni(OH) + 6H green ppt. equilibrium 2 [Ni(H + 6NH [Ni(NH + 6H blue Use Le Chatelier's principle to suggest explanations for the following observations.

Q3(i)

Short Answer 1 mark

Explain why when aqueous NH is added dropwise to [Ni(H a green precipitate is formed.

Q3(ii)

Short Answer 1 mark

Explain why when a large excess of aqueous NH is added to [Ni(H , the green precipitate dissolves and a blue solution is formed.

Q3(d)

Short Answer 1 mark

The complex ion [NiBr

Q3(cn)

Short Answer 1 mark

shows stereoisomerism. Draw diagrams to show the two isomers of [NiBr

Q3(cn)

Short Answer 1 mark

. Name the type of stereoisomerism. isomer 1 isomer 2 type of stereoisomerism [2] [Total: 9]

Q4(a)

Short Answer 2 marks

(i) When benzene undergoes nitration a nitro group substitutes at a carbon atom. State the shape (geometry) around the substituted carbon atom

Q4(ii)

Short Answer 1 mark

Naphthalene, C , is an arene hydrocarbon. naphthalene When naphthalene undergoes nitration, a mixture of two organic compounds is formed. Each compound contains one nitro group. Suggest the structures of these compounds. structure 1 structure 2

Q4(b)

Short Answer 1 mark

Naphthalene can be oxidised under certain conditions to phthalic anhydride, C carbon dioxide and water. Construct an equation for this reaction. Use [O] to represent an atom of oxygen from the oxidising agent.

Q4(c)

Short Answer 1 mark

The indicator, phenolphthalein, can be synthesised from phthalic anhydride and phenol under certain conditions. phthalic anhydride phenolphthalein phenol O2+ Deduce the type of reaction shown by this equation.

Q4(d)

Short Answer 1 mark

(i) Name the functional groups, in addition to the benzene ring, present in a phenolphthalein molecule.

Q4(ii)

Short Answer 1 mark

Phenolphthalein reacts separately with the two reagents shown in the table. Complete the table by: given for you) reagent organic product structure type of reaction an excess of hot NaOH(aq) an excess of

Q4(e)

Short Answer 2 marks

Phenolphthalein is an indicator and is represented by the formula HIn. Phenolphthalein, HIn, is a weak acid.HIn + In The K value for phenolphthalein is 5.0 × 10-10 at a pH of approximately 8.8. Calculate the ratio [In [HIn] at pH 8.8. ratio [In [HIn] =

Q4(f)

Short Answer 1 mark

Methyl orange is another acid-base indicator. Its structure in aqueous solution at pH 4.4 is shown. NN SO methyl orange

Q4(i)

Short Answer 1 mark

On the structure of methyl orange, circle the bond or bonds that make this compound a dye.[1] The colour of this indicator changes between pH 3.2 and pH 4.4.

Q4(ii)

Short Answer 1 mark

Suggest the structure of methyl orange at pH 3.0. Assume the -SO group is unreactive.

Q4(g)

Short Answer 1 mark

Methyl orange can be synthesised as shown. NN SO methyl orange step 2 step 1

Q4(i)

Short Answer 2 marks

Deduce the identities of compounds R and S and draw their structures in the boxes.

Q4(ii)

Short Answer 1 mark

Suggest reagents and conditions for step 1 and step 2. step 1 . step 2 . [3] [Total: 19]

Q5(a)

Short Answer 1 mark

Define the term partition coefficient, K

Q5(b)

Short Answer 2 marks

K of water. Calculate the mass of benzoic acid extracted into the water layer. mass of benzoic acid extracted = g

Q5(ii)

Short Answer 1 mark

K of benzophenone, CCOC value of K of benzoic acid given in (b)(i). Explain why.

Q5(c)

Short Answer 1 mark

Benzophenone can be synthesised from benzoic acid in two steps as shown. In step 1 compound J, a reactive reaction intermediate, is formed. Compound J then reacts with an organic compound, K, to form benzophenone. Al Cl step 1 benzoic acid benzophenone

Q5(i)

Short Answer 2 marks

Deduce the identities of organic compounds J and K and draw their structures in the boxes.

Q5(ii)

Short Answer 1 mark

Suggest reagents and conditions for step 1.

Q5(d)

Short Answer 1 mark

Benzophenone can also be synthesised in two steps from bromomethylbenzene. L, C step 3 bromomethylbenzene step 4KMnO , heat benzophenone

Q5(i)

Short Answer 1 mark

Deduce the identity of compound L and draw its structure in the box.

Q5(ii)

Short Answer 2 marks

Name the mechanism of step 3 and suggest reagents and conditions for step 3. mechanism of step 3 reagents and conditions

Q5(iii)

Short Answer 1 mark

Deduce the type of reaction in step 4. benzophenone. number of peaks

Q5(ii)

Short Answer 1 mark

Identify two different environments of carbon atom that would result in different chemical environment of carbon atom chemical shift range (δ) [2] [Total: 15]

Q6

Short Answer 1 mark

The class of polymers called polycarbonates are made by the reaction of carbonyl dichloride, , with a diol. n HOROH + n COCl +2nHClO a diol a polycarbonate

Q6(a)

Short Answer 1 mark

(i) Deduce the type of polymerisation shown here. Nalgene HO OH

Q6(ii)

Short Answer 1 mark

Draw one repeat unit of Nalgene

Q6(iii)

Short Answer 1 mark

Nalgene is a strong and tough polymer. Identify two types of intermolecular force that are responsible for these properties of Nalgene 1 2

Q6(b)

Short Answer 2 marks

Proteins are polymers of amino acids. Complete the table to show how the secondary and tertiary structures of proteins are stabilised. one intermolecular force responsible groups involved secondary structure tertiary structure

Q6(c)

Short Answer 1 mark

Explain the significance of hydrogen bonding in DNA in relation to the accurate replication of genetic information.

Q6(d)

Short Answer 1 mark

Many polymers are degradable. State two different processes by which some polymers can be degraded.

Q6(e)

Short Answer 1 mark

The cyclic peptide B is shown. Cyclic peptide B is broken into its monomers by heating under reflux with dilute hydrochloric acid. The amino acid threonine, Thr, and two other organic products are formed. threonine

Q6(i)

Short Answer 2 marks

Draw the structures of the two other organic products formed.

Q6(ii)

Short Answer 1 mark

Using the 3-letter abbreviations for the amino acids as given in the Data Booklet, complete the sequence for the cyclic peptide, B.Thr

Q6(iii)

Short Answer 1 mark

Name two analytical techniques that could be used to separate these amino acids. [Total: 12]

Q7(a)

Short Answer 1 mark

(i) Define the term electron affinity.

Q7(ii)

Short Answer 1 mark

Define the term lattice energy .

Q7(b)

Short Answer 1 mark

Use the following data and relevant data from the Data Booklet to calculate a value for the enthalpy change of formation of zinc bromide, ZnBr

Q7(s)

Structured 4 marks

You might find it helpful to construct an energy cycle. enthalpy change of vaporisation of Br lattice energy of ZnBr enthalpy change of formation of ZnBr

Q7(c)

Short Answer 1 mark

The lattice energies of ZnBr and ZnO are shown. ZnBr -2678 -2734 ZnO -3971

Q7(i)

Short Answer 1 mark

Explain why there is a difference between the lattice energies of ZnBr and ZnO. [Total: 10]

Q8(a)

Short Answer 1 mark

(i) Define the term standard cell potential . An electrochemical cell is set up to measure the standard electrode potential of a cell, , made of a Co half-cell.

Q8(ii)

Short Answer 1 mark

Complete the table with the substance used to make the electrode in each of these half-cell electrode

Q8(iii)

Short Answer 1 mark

Use data from the Data Booklet to calculate the = V

Q8(iv)

Short Answer 1 mark

Write the equation for the overall cell reaction.

Q8(b)

MCQ 1 mark

A fuel cell is an electrochemical cell that can be used to generate electrical energy. A methanol-oxygen fuel cell can be used as an alternative to a hydrogen-oxygen fuel cell. When the cell operates, the carbon atoms in the methanol molecules are converted into carbon dioxide. OH + H + 6H + 6e Calculate the volume of CO , in cm 30 minutes. Assume the cell is operated at room conditions. volume of CO = cm [2] [Total: 7] Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge.

A

fuel cell is an electrochemical cell that can be used to generate electrical energy.

A

methanol-oxygen fuel cell can be used as an alternative to a hydrogen-oxygen fuel cell.

Board	CAIE
Level	A Level
Subject	Chemistry
Code	`9701`
Year	2020
Session	May/June
Q&A	67 questions

Chemistry 2020 · May/June

Questions & Model Answers 67 Qs

Paper Details