JJC_H2 Chemistry Prelim P2 Question

JURONG JUNIOR COLLEGE PRELIMINARY EXAMINATION 2008 H2 CHEMISTRY PAPER 2 9746 / 2 Friday 22 nd August 2008 1 hour 30 minutes Name: ______________________ ( No. ________) Class: 07_____ INSTRUCTIONS TO CANDIDATES Do not open this booklet until you are told to do so. Write your name, exam index number and class in the spaces at the top of this page. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a pencil for any diagrams, graphs, or rough working. Do not use highlighters or correction fluid. Answer all questions. INFORMATION FOR CANDIDATES A Data Booklet is provided. Do not write anything on the Data Booklet. The number of marks is give n in brackets [ ] at the end of each question or part question. You are advised to show all workings in calculations. You may use a calculator. FOR EXAMINER’S USE 1 2 3 4 5 6 TOTAL / 60 This question paper consists of 13 printed pages, including this page. [Turn over

Page 2 of 13 1. Many copper minerals are found in hy drothermal deposits where they were formed by crystallisation from very hot solutions. Deep underground, it is like a giant pressure cooker and water is still in liquid form at high temperature. This means that minerals which are regarded as ‘insoluble’ in the laboratory can dissolve under these cond itions. When the solutions cool, the minerals crystallise out. One such copper mineral is chalcopyrite, CuFeS 2, which is a copper iron sulfide mineral that crystallises out in a tetragonal system. Chalcopyrite is one of the minerals referred to as ‘Fool's Gold’ due to its brassy yellow appearance. (a) Chalcopyrite can be smelted in modern works by heating with air. 3CuFeS2 + 8O2 Æ 3Cu + FeO + Fe2O3 + 6SO2 A rock sample was found to contain 0.5 % by mass of chalcopyrite. (i) Calculate the volume of sulfur dioxide gas released into the atmosphere at r.t.p. if 1 tonne of the rock sample is smelted. (1 tonne = 1000 kg) (ii) Suggest a reason why we should try to limit the emission of sulfur dioxide into the atmosphere. ……………………………………………………………………………… ……………………………………………………………………………… [4]

1. Chalcanthite, known as ‘copper flower’, is a water soluble copper sulfate mineral. When dissolved, aqueous copper(II) sulfate contains [Cu(H2O)6]2+ ions. (b) Water is a simple molecule. The H −O−H bond angle in an isolated water molecule is 104.5 °. The diagram below shows part of the [Cu(H 2O)6]2+ ion and the H −O−H bond angle in the water ligand. H Cu 2+ O H (i) Explain why the H–O–H bond angle in the water ligand is 107 ° while that in an isolated water molecule is 104.5 °. ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… …………………………………………………………