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’. …………………………………………………………………………………… …………………………………………………………………………………… (ii) Write down the expression for Ka of ethanoic acid [2] [Total : 6] 3. The rate of reaction is affected by factors such as temperature and catalyst. (a) With the help of an appropriate sketch of the Boltzmann distribution, explain how the increase in temperature speeds up a chemical reaction. [3] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… ……………………………………………………………………………………………

5 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 (b) Other than temperature and catalyst, suggest and explain another factor which will affect the rate of reaction. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… (c) Aluminium oxide is a common oxide which is insoluble in water and amphoteric in nature. (i) Define the term amphoteric …………………………………………………………………………………… …………………………………………………………………………………… (ii) Describe two reactions which show the amphoteric behaviour of aluminium oxide. …………………………………………………………………………………… …………………………………………………………………………………… (iii) Explain why aluminium oxide is insoluble in water. [5] …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… [Total : 10 ]

6 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 4. There are some wines that taste better after a period of ‘ageing’ process. After ageing, the wine is said to taste more flavourful and is more appealing to consumers. One of the many reactions that takes place in the wine is the alcohol (ethanol) reacting with the fruit acids. Reaction (1): RCOOH(aq) + CH2CH3OH(aq) = RCOOCH2CH3(aq) + H2O(l) where RCOOH represents the fruit acids. The ageing process usually involves placing the wine bottles in a cold environment (about 13 °C) for period of about 1 year. In time, the ester that is produced will give the ‘flavour’ that aged wine has. However, th e wine can be easily ‘damaged’ if the bottles are exposed to high heat, even for short periods of time. When this happens, the wine becomes sour. Wine can also be ‘damaged’ if it is exposed to the air. In this case, the alcohol (ethanol) inside the wine is converted to ethanoic acid by oxygen in the air (where oxygen is converted to water). This event may happen during the bottling stage, where air is unintentionally introduced into the bottle. (a) (i) ‘...placing the wine bottles in a cold environment...’ From this statement, what can you deduce about the enthalpy change of reaction (1)? Explain your answer. …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… (ii) Hence, explain why “... the wine can be easily ‘damaged’ if the bottles are exposed to high heat, even for short periods of time... becomes sour to the taste.”, paying particular attention to the underlined phrases. [5] …………………………………………………………………………………… …………………………………………………………………………………… …………………………………………………………………………………… (b) (i) By means of two half equation s, write a full balanced equation for the oxidation of ethanol to ethanoic acid.

7 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 (ii) During a bottling process, 8 cm 3 of air is introduced accidentally into a 750 cm3 wine bottle. What is the maximum concentration (in mol dm−3) of ethanoic acid that can be produced? Assume that ethanol is in excess and air contains 20% oxygen [4] [Total : 9] 5 (a) The diagram below shows the synthesis pathway starting with propene:

8 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 CH3CH OH CH3 CH3 C O CH3 CH3 C OH CN CH3 CH3 C OH C O OH CH3 step 1 step 2 step 3 step 4 CH3 C OH C O O CH CH3 CH3 CH3 KMnO4 and H2SO4 Heat step 5 CH3CH CH2 H2SO4 Heat Concentrated (i) State the reagents and conditions for step 1 and 3. …………………………………………………………………………………… …………………………………………………………………………………… (ii) Draw the structure of the products of step 2 and 5. (iii) Name the type of reaction taking place in step 5. [5] …………………………………………………………………………………… (b) Suggest a simple chemical test to distinguish the following pairs of compounds. Your answers should include the reagents and conditions for each

9 River Valley High School 8872/02/PRELIM/12 [Turn over Preliminary Examination 2012 test and the observations you would expect to see for each compound. (i) Cl and I …………………………………………………………………………………………… ………