Cambridge International AS & A Level

1 Cambridge International AS & A Level *0123456789*. CHEMISTRY 9701/04. Paper 4 A Level Structured Questions For examination from 2022. SPECIMEN PAPER 2 hours You must answer on the question paper. No additional materials are needed. INSTRUCTIONS. Answer all questions. Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. Write your name, centre number and candidate number in the boxes at the top of the page. Write your answer to each question in the space provided. Do not use an erasable pen or correction fluid. Do not write on any bar codes. You may use a calculator.

2 You should show all your working and use appropriate units. INFORMATION. The total mark for this paper is 100. The number of marks for each question or part question is shown in brackets [ ]. The Periodic Table is printed in the question paper. Important values, constants and standards are printed in the question paper. This document has 24 pages. Blank pages are indicated. UCLES 2019 [Turn over 2. 1 (a) (i) State what is meant by partition coefficient.. [2]. Ammonia is soluble in both water and organic solvents. An aqueous solution of ammonia is shaken with the immiscible organic solvent trichloromethane.]

3 The mixture is left to reach equilibrium. Samples are taken from each layer and titrated with dilute hydrochloric acid. A cm3 sample from the trichloromethane layer requires cm3 of mol dm 3. HCl to reach the end-point. A cm3 sample from the aqueous layer requires cm3 of mol dm 3 HCl to reach the end-point. (ii) Calculate the partition coefficient, Kpc, of ammonia between trichloromethane and water. Show your working. Kpc = .. [2]. (iii) Butylamine, C4H9NH2, is also soluble in both water and organic solvents. Suggest how the numerical value of Kpc of butylamine between trichloromethane and water would compare to the value of Kpc calculated in (a)(ii).

4 Explain your answer.. [2]. (b) Butanamide, C3H7 CONH2, is much less basic than butylamine. Explain why.. [1]. [Total: 7]. UCLES 2019 9701/04/SP/22. 3. 2 The feasibility of a chemical reaction depends on the standard Gibbs free energy change, G . This is dependent on the standard enthalpy and entropy changes, and the temperature. (a) State and explain whether the following processes will lead to an increase or decrease in entropy. (i) the reaction of magnesium with hydrochloric acid entropy change .. explanation .. [1]. (ii) the dissolving of solid potassium chloride in water entropy change .. explanation.

5 [1]. (iii) the condensing of water from steam entropy change .. explanation .. [1]. (b) Magnesium carbonate can be decomposed on heating. MgCO3(s) MgO(s) + CO2(g) H = +117 kJ mol 1. Standard entropies are shown in Table Table substance MgCO3(s) MgO(s) CO2(g). S / J K 1 mol 1 + + +214. (i) Calculate G for this reaction at 298 K. Show your working. G = .. kJ mol 1 [3]. (ii) Explain why this reaction is feasible only at high temperatures.. [1]. UCLES 2019 9701/04/SP/22 [Turn over 4. (c) Table lists values of solubility products, Ksp, of some Group 2 carbonates. Table solubility product in water at 298 K, Ksp / mol2 dm 6.]

6 MgCO3 10 5. CaCO3 10 9. SrCO3 10 10. Deduce the trend in the solubility of the Group 2 carbonates down the group. Justify your answer using the data given.. [1]. (d) (i) Write an equation to show the equilibrium for the solubility product of MgCO3. Include state symbols.. [1]. (ii) With reference to your equation in (d)(i), suggest what is observed when a few cm3. of concentrated Na2CO3(aq) are added to a saturated solution of MgCO3. Explain your answer.. [2]. (e) Use the data in Table to calculate the solubility of MgCO3 in water at 298 K, in g dm 3. Show your working. solubility of MgCO3 =.

7 G dm 3 [2]. UCLES 2019 9701/04/SP/22. 5. (f) Describe and explain the variation in the thermal stabilities of the carbonates of the Group 2. elements.. [3]. [Total: 16]. UCLES 2019 9701/04/SP/22 [Turn over 6. 3 (a) The initial rate of the reaction of chlorine dioxide, Cl O2, and fluorine, F2, is measured in a series of experiments at a constant temperature. 2Cl O2 + F2 2Cl O2F. The results obtained are shown in Table Table experiment [Cl O2] / mol dm 3 [F2] / mol dm 3 initial rate /. mol dm 3 s 1. 1 10 3. 2 to be calculated 3 to be calculated 10 3. The rate equation is rate = k[Cl O2][F2]. (i) Explain what is meant by order of reaction with respect to a particular reagent.]

8 [1]. (ii) Use the results of experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. k = .. units .. [2]. (iii) Use the data in Table to calculate the initial rate in experiment 2. initial rate = .. mol dm 3 s 1 [1]. (iv) Use the data in Table to calculate [Cl O2] in experiment 3. [Cl O2] = .. mol dm 3 [1]. UCLES 2019 9701/04/SP/22. 7. (b) (i) Explain what is meant by rate-determining step.. [1]. (ii) The mechanism of the reaction between Cl O2 and F2 has two steps. Suggest equations for the two steps of this mechanism. step 1 .. step 2 .. [1]. (iii) State and explain which of the two steps is the rate-determining step.

9 Rate-determining step = .. [1]. (c) Describe the effect of temperature change on the rate of a reaction and the rate constant.. [1]. [Total: 9]. UCLES 2019 9701/04/SP/22 [Turn over 8. 4 (a) 4-nitromethylbenzene can be prepared via an electrophilic substitution reaction as shown in Fig. methylbenzene intermediate T 4-nitromethylbenzene CH3 CH3 CH3. conc. HNO3. conc. H2SO4. H NO2 NO2. Fig. (i) This reaction also forms an isomer of 4-nitromethylbenzene as a by-product. Draw the structure of this by-product. [1]. (ii) Write an equation for the reaction between HNO3 and H2SO4 that forms the electrophile for this reaction.]

10 [1]. (iii) Describe how the structure and bonding of the six-membered ring in intermediate T differ from those in methylbenzene. In your answer refer to the hybridisation, the bonding and the bond angles in the ring system.. [3]. UCLES 2019 9701/04/SP/22. 9. (b) Benzocaine is used as a local anaesthetic. It can be synthesised from 4-nitromethylbenzene by the route shown in Fig. 4-nitromethylbenzene CH3 CH3 CH3. step 1 step 2. NO2 NH2 NHCOCH3. step 3. benzocaine W. COOCH2CH3 COOH COOH. CH3CH2OH step 4. NH2 NH2 NHCOCH3. Fig. (i) Give the systematic name of compound W.. [1]. (ii) Suggest the reagents and conditions for step 1.