NJC_Structured Paper Prelim

Registration Number ST group Name NATIONAL JUNIOR COLLEGE H1 Chemistry Preliminary Examination CHEMISTRY PAPER 2 21 August 2008 TIME: 2 hours INSTRUCTIONS TO CANDIDATES Do not open this booklet until you are told to do so. Write your name, class and registration number in the spaces provided at the top of this page. Do not open this booklet until you are told to do so. Write your name, class and registration number in the spaces provided at the top of this page. Section A: Answer ALL questions in the spaces provided on the question paper. The number of marks is given in brackets [ ] at the end of each question or part question. Section B: Answer any two questions on the writing paper provided. Begin each question on a fresh sheet of paper. Staple your answers at the back of this booklet. Circle the questions answered on the cover page of this booklet. The number of marks is given in brackets [ ] at the end of each question or part question. INFORMATION FOR CANDIDATES A Data Booklet is provided. You may use a calculator. For Examiner’s Use Section A 1 / 9 2 / 9 3 / 12 4 / 10 Section B 5 / 20 6 / 20 7 / 20 Total P2 This question paper consists of 10 printed pages (including this page).

Section A: Structured Questions (40 Marks) 1. Use of Data Booklet is relevant to this question. Gallium was first discovered by Lecoq de Boisbaudran in 1875 when he was studying zinc blende from the Pyrennees. In present day, it is now widely distributed in minute quantities and is used in thermometers for temperatures up to 100 0C, where it is an alloy with indium and tin in liquid state. It is also used in the semi- conductor industry in the manufacture of diodes and transistors. (a) (i) Describe the relative charges and masses of protons, neutrons and electrons. Explain fully how these particles are arranged in a Gallium atom. [3] (ii) State the number of protons, electrons and neutrons in an atom of 69Ga. [1] (b) Gallium exists as two isotopes, 69Ga and 71Ga in the proportion of 3:2. (i) Define the term isotope. [1] (ii) Calculate the relative atomic mass of gallium. [2] (iii) A gaseous mixture of 69Ga3+ and 71Ga3+ is passed through an electric field which is at right angles to their direction of travel. State and explain which one of the two ions will be deflected to a larger angle. [2] [Total: 9] 2

2. Nitrogen monoxide can be produced by the oxidation of ammonia according to the equation below. 4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (g) (a) (i) The NO bond energy in nitrogen monoxide is 607 kJ mol –1. Explain what is meant by the term bond energy with reference to the NO molecule. [1] (ii) Calculate the enthalpy change for the reaction above using (a)(i) and other bond energy values from the Data Booklet.