2021 RVHS Prelim P2 Qns

River Valley High School 2021/8873/02 [Turn over 2021 JC 2 Preliminary Examination Paper 2 RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 2 0 J CENTRE NUMBER S INDEX NUMBER H1 CHEMISTRY 8873/02 Paper 2 Structured Questions 15 Sep 2021 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 pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the space provided. Section B Answer one question in the space provided. A Data Booklet is provided. Do NOT write anything on it. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Paper 1 30 Paper 2 1 9 2 7 3 6 4 5 5 18 6 15 7 20 8 20 s.f. units Paper 2 80 Total 110 This paper consists of 20 printed pages.

2 River Valley High School 2021/8873/02 2021 JC 2 Preliminary Examination Paper 2 Section A (60 marks) Answer all the questions in this section. 1 (a) (i) Describe the reactions, if any, of the chlorides MgC l2 and PCl5 with water. Write equations for all reactions that occur, and suggest the pH of the resulting solutions. Relate the reactivity of the se chlorides to their structure and bonding. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [3] (ii) Carbon is in the same group as silicon. Suggest and explain if CC l4 will react with water. ……………………………………………………………………………… ……………………………………………………………………………… [1] (b) Phosphorus exist as 31P, 32P and 33P isotopes. 31P is the most stable isotopes. (i) Define the term isotopes. ……………………………………………………………………………… ……………………………………………………………………………… [1]

3 River Valley High School 2021/8873/02 [Turn over 2021 JC 2 Preliminary Examination Paper 2 (ii) 31P can react with chlorine to form phosphorus chloride. Phosphorus in phosphorus chloride can exhibit variable oxidation states. Based on your knowledge in periodicity, state the two common oxidation states of phosphorus in phosphorus chloride ……………………………………………………………………………… [1] (iii) Phosphorus can exist as cations or anions. The angle of deflection for a beam of 31P+ ions in an electric field is 6. Calculate the angle of deflection for a beam of 33P3 ions in the same electric field and show in the diagram below, Fig 1, how a beam of 33P3 ions will deflect in the electric field. Fig. 1 [2] (iv) 32P is unstable and decays rapidly to another element. During the decay, a neutron is converted to a proton with the release of an electron, forming a charged ion. Write an equation to show the reaction. ……………………………………………………………………………… [1] [Total : 9]  + Beam of 33P3 ions

4 River Valley High School 2021/8873/02 2021 JC 2 Preliminary Examination Paper 2 2 (a) Propanoic acid is a weak acid and can be used to make a buffer solution. (i) State the difference between a weak acid and a strong acid. ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... [1] (ii) Explain what is meant by the term buffer solution. ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... [1] (iii) The hydrogencarbonate ion, HCO 3, is part of the buffer in the blood. Write an equation showing how HCO 3 reacts with acid in the blood. ………………………………………………………………………....... [1] (iv) After consuming food or drink containing sugar, the pH in the mouth can drop from pH 6.8 to a pH of approximately 4.8 as the sugar is broken down into lactic acid. In time, hydrogencarbonate ions in saliva restore the pH to its original value. Define pH and c alculate the H + ion concentration in the mouth at pH 4.8. ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... [2] (b) Write an equation for the reaction between propanoic acid and sodium hydroxide. Label the conjugate acid and the conjugate base in your equation. ………………………………………………………………………....... ………………………………………………………………………....... [2] [Total: 7]

5 River Valley High School 2021/8873/02 [Turn over 2021 JC 2 Preliminary Examination Paper 2 3 When 40 cm 3 of a gaseous organic compound, C xHyO, underwent complete combustion with an excess of oxygen, the total volume reduced by 130 cm3. A further contraction of 200 cm 3 took place when the residual gas was passed through aqueous sodium hydroxide. All volumes were measured at 25 C and 1 atm. (a) Write a balanced equation for the complete combustion of CxHyO. ……………………………………………………………………….................. [1] (b) State the function of NaOH(aq). ……………………………………………………………………….................. [1] (c) (i) State the volume of CO2 produced in this reaction ………………………………………………………………………....... [1] (ii) Hence, determine the values of x and y. [3] [Total: 6]

6 River Valley High School 2021/8873/02 2021 JC 2 Preliminary Examination Paper 2 4 Magnesium oxide is available for purchase without a prescription. It is added to dietary supplements as well as over -the-counter medications used to treat constipation, indigestion, and headaches. (a) Using the given Born-Haber cycle for the formation of MgO(s), the following data given as well as data from the Data Booklet, calculate the lattice energy of MgO(s). sum of 1st and 2nd electron affinity of oxygen +702 kJ mol–1 enthalpy change of formation of magnesium oxide 602 kJ mol–1 [2] (b) Predict and explain how the lattice energy of Mg 3N2 will differ as compared to MgO. ………………………………………………………………................................. ………………………………………………………………................................. ………………………………………………………………................................. ………………………………………………………………................................. ………………………………………………………………................................. ………………………………………………………………................................. ………………………………………………………………................................. [3] [Total: 5] Mg(s) + ½ O2(g) MgO(s) Mg (g) O (g) Mg2+(g) + O2(g) +168 LE(MgO) = ?

7 River Valley High School 2021/8873/02 [Turn over 2021 JC 2 Preliminary Examination Paper 2 5 Chemists use ideas of collisions and rates of reaction to help them be more efficient when manufacturing chemicals on a large scale. One such process is the Haber process for the production of ammonia. The enthalpy change of the reaction is 46 kJ per mole of ammonia. (a) (i) Write an equation to show the chemical reaction that happens in the Haber process. ………………………………………………………………………....... [1] (ii) Define the term heterogeneous catalyst. ………………………………………………………………………....... ………………………………………………………………………....... ………………………………………………………………………....... [1] (iii) Name the catalyst used in the Haber process. ………………………………………………………………………....... [1] (iv) State the conditions used in the Haber process. ………………………………………………………………………....... [1] (v) Describe and e