RVHS Prelim P2 QP

1 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS CENTRE NUMBER S 3 0 4 4 INDEX NUMBER H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 12 Sep 2018 2 hours Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST. DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO. Write your name, class and index number in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. PAPER 2 QUESTION 1 9 QUESTION 2 9 QUESTION 3 8 QUESTION 4 14 QUESTION 5 12 QUESTION 6 10 QUESTION 7 13 Units s.f. PAPER 1 PAPER 2 PAPER 3 TOTAL PAPER 4 GRADE 30 75 80 185 55 This paper consists of 20 printed pages.

2 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations Answer all questions in the spaces provided. 1 Magnesium, aluminium, W and X are 4 different elements in the 3 rd Period. The following are some of their properties: The chloride of W dissolves in water to give a strongly acidic solution and the oxide of W. The chloride of X reacts with ethanoic acid to fo rm ethanoyl chloride as one of the products. (a) Identify the elements, W and X, and write the balanc ed equations for the reactions described above. W: ………………………… Chloride of W dissolved in water (equation): ……………………………………………………………………………………… X: ………………………… Chloride of X reacting with ethanoic acid (equation): ……………………………………………………………………………………… [2] (b) Aluminium oxide is a white solid that is soluble in NaOH(aq) to give a colourless solution. ( i ) Write a balanced equation, with st ate symbols, to describe the reaction of aluminium oxide with NaOH(aq). ……………………………………………………………………………………… [1]

3 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations ( i i ) Describe the observations made when HC l(aq) is carefully added to this colourless solution, until HCl(aq) is in excess. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2] (c) State and explain how the decom position temperature of BaCO 3 compares with that of MgCO3. ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... [3] (d) Explain why the 1 st ionisation energy of aluminium is of lower magnitude compared to that of magnesium. ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... [1] [Total: 9]

4 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations 2 Pyridine C 5H5N is a weak alkali with a distinct ive, unpleasant fish-like smell. Pyridine reacts readily with hydrochloric acid to form pyridinium chloride only. Pyridinium chloride is commercially available in a form of 98.0% purity by mass. pyridine pyridinium Pyridinium chloride has a pKa value of 5.25. (a) Calculate the mass of 98.0% pyridi nium chloride that must be added to 1.00 dm3 of water to give a solution of pH 3.5. (You may assume no change in volume of solution upon addition of the salt.) [3]

5 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations (b) Calculate the pH of the reaction mixture when 5.00 cm 3 of 0.0125 mol dm –3 hydrochloric acid is added to 25.00 cm3 of 0.100 mol dm–3 of pyridine. [3] (c) With the aid of two equations, explain how a solu tion of pyridinium chloride and pyridine can control pH. ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... [3] [Total: 9]

6 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations 3 Nitrosoyl chloride, NOC l, is a yellow gas that c an be formed between nitryl chloride and nitric oxide in the following reversible reaction: NO2Cl(g) + NO(g) ⇌ NOCl(g) + NO2(g) ΔH is negative (a) A 3:1 molar ratio mixture of NO 2Cl(g) and NO(g), at a total initial pressure of 5 atm, was allowed to react in a clos ed vessel at 800 K. When equilibrium was reached at time t1, the partial pressure of NO 2Cl was found to be 2.90 atm. Calculate the value of the equilibrium constant, Kp, of the reaction at 800 K. [2] (b) At time t 2, more NO2Cl gas was introduced into the vessel at 800 K, causing the partial pressure of NO 2Cl to increase to 3.25 atm. The system was allowed to reach equilibrium befor e the temperature was increased to 1000 K at t3. A new equilibrium was established at t4. In the pressure-time axes below, sketch the graph that would be observed from time = 0 to time = t4, clearly indicating the values of the partial pressure of NO2Cl at time = 0, t1 and t2. [2] PNO2Cl / atm time / min 0

7 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations (c) Given that nitrogen is the central atom, draw the do t-and-cross diagram for NOCl. [1] (d) NOCl reacts with CH 3CH=CH2 to give a product as predicted by Markovnikov’s rule. When the organi c product is heated with NaOH(aq), followed by acidification and addition of AgNO 3(aq), a white precipitate is obtained. Given that the oxidation state of chlorine in NOC l is +1, state and draw the mechanism for the reaction between NOCl and CH3CH=CH2. [3] [Total: 8]

8 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations 4 (a) Sucrose, or table sugar, is the most common natural food sweetener. In acidic medium, sucrose is readily hy drolysed to a mixture of glucose and fructose. The reaction is also acid-catalysed. C 12H22O11 + H2O C6H12O6 + C6H12O6 A series of experiments was carried out at room temperat ure to investigate the kinetics of this reaction, using 0.850 mol dm −3 sucrose solution and 1.23 mol dm−3 hydrochloric acid. Expt Volume of sucrose / cm3 Volume of HCl / cm3 Volume of water / cm3 Initial rate of reaction / mol dm−3 min−1 1 20 30 0 1.77 × 10−3 2 20 20 10 1.18 × 10−3 3 10 30 10 8.85 × 10−4 4 40 20 10 ? ( i ) Using the data given above, determi ne the order of reaction with respect to sucrose and HCl. ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... [2] H+(aq) (sucrose) (fructose)

9 River Valley High School 9729/02 [Turn over 2018 Preliminary Examinations ( i i ) Hence, write the rate equation and deduce the rate constant of the reaction, stating its units. ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... ………………………………………………………………………………... [2] ( i i i ) Using your answer in (a)(ii), calculate the initial rate of reaction for Experiment 4. ………………………………………………………………………………... ………………………………………………………………………………... ……