Chemistry Matters for G.C.E. ‘O’ Level
Chapter 4
Chapter 4
Elements, Compounds and Mixtures
Answers to Textbook Exercises Test Yourself 4.1 (page 63) 1. (a) Mg and Mn (b) (b) S and and Si (c) Zn and Sn 2. Hydrogen H, phosphorus P, sulphur S, chlorine C l, calcium Ca, iron Fe, aluminium A l, oxygen O, silicon Si 3.
• • •
4.
• • •
Poor conductor of heat Dull looking Brittle Ductile and malleable Good conductor of electricity Solid at r.t.p.
Quick Check (page 66) 2:1
Test Yourself 4.2 (page 67) 1. (a) (i) Co, Cu (ii) AlF3, CoO, CO, NaBrO 3, Na2S, V2O5, CaSO4 (b) AlF3 : aluminium, fluorine CoO : cobalt, oxygen CO : carbon, oxygen NaBrO3 : sodium, bromine, oxygen Na2S : sodium, sulphur V2O5 : vanadium, oxygen CaSO4 : calcium, sulphur, oxygen (c) (i) AlF3, CoO, CO, Na 2S, V2O5 (ii) NaBrO 3, CaSO4 2. (a) 3
(b) 0
(c) 1
(d) 4
(e) 10
(f) 8
3. K : Cr : O = 2 : 2 : 7 4. Na2SiO3
Quick Check (page 68) Nitrogen, oxygen, argon, carbon dioxide and water vapour. The various gases can be separated by physical means.
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Chemistry Matters for G.C.E. ‘O’ Level
Chapter 4
Test Yourself 4.3 (page 69) 1. (a) B – oxygen is O 2 and will consist of the same molecule. (b) C – chlorine is C l2, therefore there will be two types of molecules, each containing two atoms. (c) A – ammonia is NH 3 and carbon dioxide is CO2. A is the only diagram that has molecules containing 3 and 4 atoms. 2.
Matter Elements
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gold dust bromine
Compounds
Mixtures
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distilled water magnesium chloride
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duralumin ink honey
Exercise 4 (page 72) Foundation 1. D
2. D
3. B
4. A
5. A
6. (a) (i) Nickel, sulphur, oxygen (ii) Copper, hydrogen, oxygen (iii) Sulphur, oxygen (b) Na3AlF6 7. (a) Carbon, hydrogen, lead (b) 8 (c) 29 8. A: hydrogen chloride
B: water
C: ammonia
D: methane
9. (a) Group 1: C 2H6, C6H6 They are compounds of carbon and hydrogen. Group 2: C2H4O2, C3H6O2 They are compounds containing three elements C, H and O. Group 3: CH 5N, NH3 These compounds contain the element nitrogen. (b) The gases in air have their individual properties. This means that the gases are not chemically combined. The proportion of the various gases in air is not fixed. The various gases can be separated by physical means.
Critical Thinking (page 73) It will be a colourless, odourless, neutral gas that is denser than air and insoluble in water. It is also unreactive and exists as single atoms. a toms.
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