MID YEAR EXAM 2011 CHEMISTRY FORM 4 PAPER 2 ( 2 ½ HOURS) SECTION A [ 60 marks ] Answer all questions in this section. 1. Diagram 1 shows the set up of apparatus to determine the melting point of substance X by heating solid X until it melts. Then the temperature of substance X is recorded every half minutes when it is left to cool at room temperature.
(a) What is the purpose of using water bath in the experiment ? …………………………………………………………………………………………………. …………………………………………………………………………………………………. (1 mark) (b) Name one substance which its melting point can be determined by using water bath. …………………………………………………………………………………………………. (1 mark)
(c) Sodium nitrate has a melting point of 310 ⁰C. Can the melting point of sodium nitrate be determined by using water bath as shown in the diagram ? Explain your answer. ………………………………………………………………………………………………… …………………………………………………………………………………………………. (2 marks)
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(d) Explain why do we need to stir the molten substance X when it is left to cool to room temperature ? ………………………………………………………………………………………………… …………………………………………………………………………………………………. (2 marks) (e) The graph of temperature against time for the cooling of molten substance X is shown in Diagram 2.
Diagram 2 (i)
State the melting point of substance X ? ………………………………………………………………………………………….......
...... (ii)
(1 mark) Explain why there is no change in temperature from Q to R.
What is the state of matter for substance X at RS ?
…………………………………………………………………………………………………. (1 mark)
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2. The boiling point and melting point of sulfur is 444 ̊C and 119 ̊C. (a) Draw the arrangement of sulfur particles at
100 ̊C
300 ̊C
600 ̊C (3 marks)
(b) Sketch a graph of temperature against time when sulphur is heated from room temperature to 200 ̊C and mark the melting point.
(2 marks) 3. A bit of liquid bromine is put into a gas jar as shown in Diagram 3 below. The gas jar is then covered with another gas jar and left for a few hours.
Liquid bromine Diagram 3 (a) What can be observed after several hours ? 3
..……………………………………………………………………………………………… (2 mark) (b) State the process that occurs. ………………………………………………………………………………………………… (1 mark) (c) Explain, using the kinetic theory of matter how the process occurs. ………..………………………………………………………………………………………... ………………………………………………………………………………………………… ………………………………………………………………………………………………… (3 marks) (d) Draw and label the atomic model proposed by Niels Bohr.
(2 marks) (e) What is the shortcoming of the model proposed by Neils Bohr ? ………………………………………………………………………………………………… (1 mark) 4. Diagram 4 shows the apparatus arrangement to determine the heat effect of copper (II) carbonate.
Diagram 4 (a) Copper (II) carbonate is heated and the gas produced is passed through lime water. (i)
State two observations after the heating performed.
………………………………………………………………………………………………… …………………………………………………………………………………………………. (2 marks) (ii)
Write the chemical equation to show the effect of heat on copper (II) carbonate.
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………………………………………………………………………………………………….. (2 marks)
(iii)Calculated the volume of gas released at room condition if 12.4 g of copper (II) carbonate is heated. [Relative atomic mass: Cu=64; C=12; O=16; molar volume: 24 dm3]
(3 marks) (b) When lead (II) nitrate aqueous solution is added to potassium iodide aqueous solution, a yellow precipitate is formed. (i)
Write a chemical equation for the reaction.
..................................................................................................................................................... (2 marks) (ii) Name the yellow precipitate. .................................................................................................................................................... (2marks) (iii) State the type of particles exist in the substance mentioned in b(ii) …………………………………………………………………………………………………... (1 mark) 5. Table 1 shows the positive and the negative ions in salt solutions. (a) Complete the table below. Name of salt Copper (II) sulphate Sodium sulphate Lead (II) nitrate Magnesium chloride
Positive ion Cu2+
Negative ion SO4 2-
Table 1 (6 marks) (b) Write the chemical formula for (i) (ii)
Sodium sulphate : …………………… Lead (II) nitrate : ..…………………… (2marks)
(c) What is another name for a positively charged ion ? 5
………………………………………………………………………………………………… (1 mark)
6. Diagram 5 shows the set up of the apparatus used in an experiment to determine the empirical formula of an oxide of copper.
Diagram 5 The following data was obtained: Mass of the combustion tube + porcelain dish Mass of the combustion tube + porcelain dish + oxide of copper Mass of the combustion tube + porcelain dish + copper
= 25.30 g = 53.30 g = 47.70 g
(a) What is meant by empirical formula ? ………….................................................................................................................................... …………................................................................................................................................. (2 marks) (b) Based on the data given (i)
Calculate the mass of copper and the mass of oxygen contained in the sample of oxide of copper. Mass of copper = ………………………… g Mass of oxygen =………………………… g (2 marks)
(ii)
Calculate the mol ratio of copper to oxygen. Given that the relative atomic mass of O=16, Cu=64.
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(2 marks) (iii)
Write the empirical formula of the oxide of copper.
………………………………………………………………………………………………… (1 mark) (c) (i) State one precautionary step to be taken while conducting this experiment. ………………………………………………………………………………………………… ………..……………………………………………………………………………………….. (1 mark) (ii) How would you make sure that all the lead oxide has been reacted with hydrogen? …………………………………………………………………………………………………. (1 mark) (d) Diagram 6 shows the structure of aspirin.
Diagram 6 (i) Write the molecular formula of aspirin. ………………………………………………………………………………………………… (1 mark) (ii) Determine the molecular mass of aspirin. [Relative atomic mass: H,1; C,12;O,16] ………………………………………………………………………………………………… (1 mark) (iii) If an aspirin pill contains 0.005 mol of aspirin, what is the mass of aspirin present in the pill? ……..…………………………………………………………………………………………… (2 mark) 7
(iv) How many molecules are there in 0.005 mol of aspirin ? [ Avogadro Constant = 6.02 X 1023 ] ………..…………………………………………………………………………………… (2 mark) SECTION B [ 20 marks ] Answer any one question from this section. 7. (a) Define the term ‘ matter ’. (1 mark) (b) Compare matter in solid, liquid and gas forms in terms of (i) the arrangement of particles (ii) the movement of particles (iii) the force of attraction between particles (9 marks) (c)
By using the kinetic theory of matter, explain the change in the state of matter when a liquid boils to form a gas. (4 marks)
(d) Using element chlorine as an example, briefly describe (i) the electron arrangements of chlorine-35 and chlorine-37 (ii) the electron arrangement of chlorine ion, Cl(6 marks) 8. (a) State the meaning of (i) Relative atomic mass (ii) One mol of a substance (iii) Molar mass (iv) Molar volume (8 marks) (b) 1 mole of any gas occupies 24 dm3 at room condition Explain why 16 g of oxygen gas occupies the same volume as 22 g of carbon dioxide at room condition. [Relative atomic mass : O=16 ; C=12 ] (4 marks) (c) Caffeine is one of the substances in coffee. 0.97 g of caffeine consists of 0.48 g carbon, 0.05 g hydrogen, 0.28 g nitrogen and 0.16 g oxygen. The molar mass of caffeine is 194 g mol-1.
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Based on the information above, determine the empirical formula and molecular formula of caffeine. [ Relative atomic mass : C=12 ; H=1 ; O=16 ; N=14] (8 marks)
SECTION C [ 20 marks ] Answer any one question from this section. 9. (a) Group 18 in the Periodic Table consists of elements known as noble gases. State the physical properties of noble gases. (2 marks) (b) The physical properties of Group 18 elements change progressively down the group. Explain briefly the change in physical properties of Group 18 elements down the group in terms of (i) Atomic size (ii) Melting point (iii) Boiling point (iv) Density of elements (8 marks) (c) Noble gases have many applications in daily life. Describe how the noble gas is useful in our daily life. (6 marks) (d) Table 2 shows the electron arrangements of the atoms of some noble gases. Element Neon Argon Krypton
Symbol Electron arrangement Ne 2.8 Ar 2.8.8 Kr 2.8.18.8 Table 2
Using the information given, explain why the elements are inert. (4 marks) 10. (a) Scientists such as Antoine Lavoisier, Johann W. Dobereiner, John Newlands, Lothar Meyer and Dmitri Mendeleev have contributed greatly to the development of the Periodic Table of elements. Describe briefly their contributions. (10 marks) (b) Explain the differences between the Periodic Table proposed by Antoine Lavoisier and the Modern Periodic Table. (6 marks) (c) The valence electron of helium is 2. Is helium a Group 2 element ? Explain why. (4 marks)
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Disemak oleh,
__________________ (Cik Premeeta Rai a/p Surase Prasad) (Guru Mata Pelajaran) Kimia)
___________________ (Pn. Norazizah Binti Abdullah) (Guru Mata Pelajaran & Ketua Panitia
