Chemistry 12 April 1996 Provincial Examination

Transcription

1 hemistry pril 996 Provincial Examination NSWER EY / SORING GIE Topics:. inetics. Equilibrium. Solubility. cids, ases, Salts. Oxidation Reduction Part : Multiple hoice Q T S GR Q T S GR I-- I-- I-- I--8 I-E- II-- II-- II-- II-- II-E- II-- II-J- II-J- III--6 III--7 III-- III-- III-- III--6 III-E- IV-- IV-- IV-- IV IV-E- IV-F-6 IV-F-9, IV-G- IV--9 IV-J- IV-J- IV-J- IV-J- IV-- IV-- IV-L- V-- V--6 V-- V-- V-- V-- V-E- V-G-, -6 V-G-9 V-- V-I- V-J- 96chpk - - January 9, 997

2 Part : Written Response Q T S GR Q T S GR I-- I-E-, II-- II-J- III--, III--6 III IV-- IV-- IV-I- IV-J- V-E- V-G-,,,, Multiple hoice = 8 (8 questions) Written Response = ( questions) Total = 80 marks LEGEN: Q = Question Number = ognitive Level T = Topic = eyed Response S = Score GR = urriculum Guide Reference = Score ox Number 96chpk - - January 9, 997

3 PRT : WRITTEN RESPONSE Value: marks INSTRTIONS: Suggested Time: 0 minutes You will be expected to communicate your knowledge and understanding of chemical principles in a clear and logical manner. Your steps and assumptions leading to a solution must be written in the spaces below the questions. nswers must include units where appropriate and be given to the correct number of significant figures. For questions involving calculation, full marks will NOT be given for providing only an answer.. a) efine the term heterogeneous reaction. ( mark) For example: reaction in which the reactants are in different phases. b) Give one example of a heterogeneous reaction. ( mark) For example: Solid Mg reacting with hydrochloric acid. 96chpk - - January 9, 997

4 . onsider the following reaction: r ( g) +O ( g) O ( g) +r ( g) Explain why the mechanism for the above reaction involves more than one step. ( mark) This is a particle collision and is unlikely to occur in one step.. onsider the following equilibrium: NO ( g) +O ( g) NO ( g) eq = 6. 0 a) Write the eq expression. ( mark) eq = [ NO ] NO [ ] [ ] O [ ] is greater than the NO [ ] at equilibrium when b) Explain why the NO the [ O ]is.0 mol L. ( mark) large eq means [ products]> [ reactants]. 96chpk - - January 9, 997

5 . onsider the following equilibrium: I ( g) ( g) +I ( g) eq = L container is initially filled with.00 mol I. alculate the [I] at equilibrium. ( marks) I + I [ I] [ ] x +x +x [ E].00 x x x [ ][ I ] eq = I [ ] x (.00 x) = 8.0 x =.897 mol L [ I]= = 0. mol L marks marks mark. Write a balanced chemical equation for the equilibrium in a saturated solution of an ionic compound with low solubility. ( marks) gl ( s) g ( aq) + + l ( aq) 6. saturated solution of g OO was evaporated to dryness. The 0.0 ml sample was found to contain.8 g g OO. alculate the solubility product constant for g OO. ( marks) 96chpk - - January 9, 997

6 Mol mass g OO = ( ) +.0 ( )+6.0 ( ) =66.9 g mol mol g OO =.8 g g OO mol g OO = 0.00 mol g 66.9 g OO 0.00 mol [ g OO]= = 0.0 mol 0.0 L L g OO marks g OO ( s) g ( aq) + + OO ( aq) sp = [ g + ][ OO ] = ( 0. 0) ( 0. 0) =. 9 0 marks (subtract mark for incorrect sig. fig) 7. Sodium phosphate, Na PO, is commonly used as a cleaning agent. Write the net ionic equation for the hydrolysis reaction between Na PO and water. ( marks) PO ( aq) + O ( l) PO ( aq) +O ( aq) 96chpk January 9, 997

7 8. alculate the p of 0.0 M OO. ( marks) OO + O O + + OO [ I] [ ] x +x +x [ E] 0.0 x x x 0.0 marks [ ][ OO ] a = O+ OO ( x) x 0.0 ( ) [ ] =.8 0 x =. 0 6 x =. 0 [ O + ]=. 0 p =.6 =.8 0 marks 96chpk January 9, 997

8 9. new indicator.. red is red when [ O + ]> 6. 0 and blue when [ O + ]<. 0. alculate the p value at the transition point for this indicator. ( marks) For example: p at 6. 0 =.0 mark p at. 0 =.60 mark Transition point p = mark =.90 mark 0. alculate the mass of NaO which is required to neutralize.00 ml of 0.00 M SO. ( marks) For example: mol SO = L 0.00 M =. 0 mol SO mark mol NaO = mass of NaO = 0.0 g mol (. 0 ) =.0 0 mol NaO mark (.0 0 ) mol =.00 g mark (subtract mark for incorrect sig. fig). alance the following half-reaction: ( marks) Sb O Sb O (basic) Sb O e Sb O + O marks Sb O + O + e Sb O + O mark 96chpk January 9, 997

9 . onsider the electrochemical cell: Volts g.0 M NO Fe.0 M g NO.0 M Fe (NO ) a) Towards which half-cell do the NO ( aq) in the salt bridge initially move? ( mark) For example: Towards Fe cell or Towards right b) Write the equation for the half-reaction occurring at the silver electrode. ( mark) g + + e g c) Identify the anode. ( mark) Fe ( s) d) What is the initial cell voltage? ( mark). V EN OF EY 96chpk January 9, 997