chemistry matters ch16 textbk ans
TRANSCRIPT
Chemistry Matters for G.C.E. ‘O’ Level Chapter 16
Chapter 16 The Periodic Table
Answers to Textbook Exercises
Test Yourself 16.1 (page 288)
(a) (2, 8, 7); Chlorine is in Period 3 and Group VII
(b) (i) C and Si (ii) Si and Cl (iii) H and Cl (iv) Cl (v) Cl
Test Yourself 16.2 (page 291)
1. Sodium
2. (a) Rubidium hydroxide (RbOH) and hydrogen (H2) (b) Rubidium chloride (RbCl)
3. (a) Rubidium (b) Lithium
Quick Check (page 292)
Halogens need one electron to obtain the noble gas structure. They can do this by sharing electrons with each other.
Test Yourself 16.3 (page 294)
(a) MgAt2
(b) Magnesium astatide
(c) Solid at room temperature and pressure.
(d) (i) Black precipitate of astatine is produced. (ii) No visible reaction
Test Yourself 16.4 (page 296)
1. They are unreactive and inert.
2. Helium is less reactive than nitrogen. Helium is less dense than nitrogen.
Exercise 16 (page 298)
Foundation
1. C 2. B 3. A 4. D 5. B 6. A 7. C
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Chemistry Matters for G.C.E. ‘O’ Level Chapter 16
Challenge
1. B 2. C
3. (a) (i) 55(b) (i) 1
(ii) Cs2O(c) (i) Caesium
(ii) 2Cs(s) + 2H2O(l) 2CsOH(aq) + H2(g)(iii) Caesium is stored in oil to prevent it from reacting with air and water.
4. (a) Number of valence electrons determines the group; number of electron shell determines period.
(b) (i) Increase in melting points / boiling pointsCl — gasBr — liquidI — solid
(ii) Decrease in reactivityCl2 can displace Br2 from NaBr(aq)Br2 can displace I2 from NaI(aq)
(c) (i) 3Br2 + 6NaOH 5NaBr + NaBrO3 + 3H2O
(ii) Reddish-brown to colourless
5. (a) (i) MnO2 + 4HCl MnCl2 + 2H2O + Cl2(ii) Oxidation number of manganese reduced from +4 to +2; oxidation number of
chlorine increased from –1 to 0. (b) (i) Colourless
(ii) Colourless
(c) At T bromine and at R iodine are formed.Cl2 (g) + 2KBr(aq) 2KCl(aq) + Br2(l)Br2(g) + 2KI(aq) 2KBr(aq) + I2(s)Cl2(g) + 2KI(aq) 2KCl(aq) + I2(s)
(d) Chlorine, bromine and iodine are poisonous.
Critical Thinking (page 300)
Reasons should include: To make the table more visual appealing and easier to understand. To make trends and patterns easier to visualize. To include also the latest discoveries about the structure of atoms. To include elements yet to be discovered. To make predictions about properties of undiscovered elements.
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