2012 RVHS_H1Chemistry Paper 2

1 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 CANDIDATE NAME CLASS 6 CENTRE NUMBER S INDEX NUMBER For Examiner’s Use Section A B6 B7 B8 Total ________________________________________________________________________________________________________ This document consists of 13 printed pages. RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION H1 CHEMISTRY 8872/02 Paper 2 11th September 2012 2 hours Candidates answer Section A on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class, Centre number and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all the questions. Section B Answer two questions on separate answer paper. 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. At the end of the examination, fasten all your work securely together.

2 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 Section A Answer all the questions in this section in the spaces provided. 1. Below is a list of elements from the third period: Period 3 Na Mg Al Si P S Cl (a) Which of these element(s) (i) have a giant metallic structure …………………………………………………………………………………… (ii) have a giant covalent structure [2] …………………………………………………………………………………… (b) Both phosphorous and silicon can react with chlorine to form PC l3 and SiCl4 respectively. Draw the dot -and-cross diagram for both compounds, state the ir shapes and suggest the values of the bond angles [3] [Total : 5 ]

3 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 2. Sulfuric acid is commonly used in various industries as a feedstock for the production of other useful chemicals such as fertilizers, synthetic resin, detergents and insecticide. (a) The contact process is the current method for producing sulfuric acid for use in various industrial processes. The main reaction of the contact pr ocess is shown: 2SO2(g) + O2(g) = 2SO3(g) ΔH = −197 kJ mol−1 An equimolar mix of SO2 and O2 is introduced into a 1 dm3 sealed flask. At equilibrium , 33.3% of O 2 is used up and the t otal amount of gas ( 2 2 3SO O SOn n n++ ) equals to 0.241 mol (i) Write down an expression for the Kc of the reaction, stating the units. (ii) Calculate the value of Kc [4]

4 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 (b) Unlike sulfuric acid, ethanoic acid, CH3COOH, is a weak acid. (i) Explain the term ‘weak acid’. ………………………………………