MI 2009_H1_CHEM_P2 Promos

Class Adm No Candidate Name: This question paper consists of 15 printed pages. Promotional Examination II 2009 Pre-university 2 H1 CHEMISTRY 8872 PAPER 2 8872 / 2 Wednesday 23 September 2009 2 h Additional materials: Answer booklet Cover page Data Booklet 5 pieces of writing paper READ THESE INSTRUCTIONS FIRST Do not open this booklet until you are told to do so. Write your name, index number and class on all the work you hand in. Write in dark blue or black pen on both sides of the writing paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluids. Section A Answer all questions. Section B Answer any two questions on the writing papers. Start each new question on a fresh sheet of writing paper. At the end of the examination, hand in your answers to Section A and Section B separately. Attach the cover page to your answer scripts for Section B. The number of marks is given in brackets [ ] at the end of each question or part question. FOR EXAMINER’S USE A B (2 questions) Total Section Q1 Q2 Q3 Q4 Q1 Q2 Q3 Marks 10 10 10 10 20 20 20 80 [Turn over

2 ( Section A Answ er ALL questions in the spaces provided. 1. (a) What do you understand by the term order of reaction? [1] .......................................................................................................................................... .......................................................................................................................................... (b) Cyanohydrins can be converted easily to useful organic acids. To form cyanohydrins, ketones are reacted with a basic solution of sodium cyanide. CH3CH2)2C=O + HCN  (CH3CH2)2C(OH)CN pentanone The above reaction was carried out with different concentrations of the three reagents and the following results were obtained and recorded in the table below. Experiment number [(CH3CH2)2C=O] / mol dm-3 [H+] / mol dm-3 [CN-] / mol dm-3 Relative initial rate 1 0.0400 0.0600 0.0600 2.000 2 0.0400 0.0400 0.0500 1.666 3 0.0500 0.0800 0.0500 2.084 A chemist determined that the order of reaction is zero with respect to hydrogen ions. Deduce the order of reaction with respect to pentanone and cyanide ions. Hence write a rate equation for the reaction. [3]

3 (c) (CH 3CH2)2C(OH)CN can be synthesized from Alcohol G by the following series of reactions. I II (CH 3CH2)2C=O (CH 3CH2)2C(OH)CN Alcohol G HCN + trace of NaOH(aq) III