2013_MI_H1_Chemistry_P2 Promos

Class Adm No Candidate Name: This question paper consists of 13 printed pages and 1 BLANK PAGE. [Turn over 2013 Promotional Examination II Pre-university 2 H1 CHEMISTRY 8872 / 02 Paper 2 Structured Questions 18 September 2013 (WEDNESDAY) Candidates answer Section A on the Question Paper. 2 hours Additional Materials: Data Booklet 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 two questions on separate answer paper. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, arrange your answers in numerical order and fasten all your work securely together. FOR EXAMINER’S USE SECTION A Q1 / 9 Q2 / 11 Q3 / 10 Q4 / 10 SECTION B Q__ / 20 Q__ / 20 Total / 80

2 SECTION A Answer all questions in the space provided. For Examiner’s Use 1. (a) Draw a dot-and-cross diagram to illustrate the bonding in H 3S+ and predict its shape. [2] (b) The bond angle of H3O+ is larger compared to that of H3S+. Explain. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ [2] (c) Acids dissociate in water to give H3O+. A solution of sulfuric acid was prepared by adding 500 cm 3 of water to a 25.0 cm 3 solution of 2.5 mol dm-3 of sulfuric acid. (i) Calculate the concentration of the sulfuric acid solution formed. (ii) Hence calculate the pH of the solution formed. [3]

3 [Turn over 1. (d) In a titration, a solution of aqueous NH 3 was titrated against the sulfuric acid solution prepared in (c). Predict if the pH at the equivalence point would be equal to, more than or less than 7. Give an equation to support your answer. For Examiner’s Use pH: ________ Equation: _________________________________________________________ [2 ] [Total: 9] 2. The term halogen, coined by a Swedish chemist Baron Jons Jakob Berzelius, refers to Group VII elements. (a) Bromine, a halogen, reacts with hot aqueous KOH according to the equation below. 3Br2(g) + 6KOH(aq) → 5KBr(aq) + KBrO3(aq) + 3H2O(l) (i) What are the oxidation states of bromine in the three bromine-containing compounds in the reaction? Br2: _____ KBr: _____ KBrO 3: _____ (ii) Hence state th