Section 1.1 Section 1.2 Section 1.3 - The Student Room

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SECTION 4 3 a DH Ca(s) + Cl 2 (g) 1 DH CaCl(s) Ca(s) + Cl 2 (g) 1 CaCl 2 (s) DH 2 DH 4 DH 2 DH 4 Ca(g) +Cl(g) DH 3 Ca + (g) + Cl – (g) Ca(g) +2Cl(g) DH 3 Ca 2+ (g) + 2Cl – (g) DH! f (CaCl) = DH 1 = DH 2 + DH 3 + DH 4 DH! f (CaCl 2 ) = DH 1 = DH 2 + DH 3 + DH 4 = (+178 kJ mol –1 + 121 kJ mol –1 ) + (+596 kJ mol –1 –355 kJ mol –1 ) + (–711 kJ mol –1 ) DH! f (CaCl) = – 171 kJ mol –1 = (+178 kJ mol –1 + 2 (+121 kJ mol –1 )) + (+596 kJ mol –1 + 1152 kJ mol –1 ) + 2 (–355 kJ mol –1 ) +(–2237kJ mol –1 ) DH! f (CaCl 2 ) = – 779 kJ mol –1 b 2DH EA (Cl) DH i (2)(Ca) +800 +600 DH i (1)(Ca) DH EA (Cl) DH i (1)(Ca) DH LE (CaCl 2 ) +400 +200 Enthalpy/kJ mol –1 1 +2200 Ca 2+ (g) + 2Cl(g) +2000 +1800 +1600 +1400 Ca 2+ (g) + 2Cl – (g) +1200 +1000 Ca + (g) + Cl(g) Ca + (g) + Cl – (g) DH at (Cl) DH LE (CaCl) 2DH at (Cl) 0 –200 DH at (Ca) DH f (CaCl) Ca(s) + Cl 2 (g) 2 CaCl(s) DH at (Ca) Ca(s) + Cl 2 (g) –400 DH f (CaCl 2 ) –600 –800 CaCl 2 (s) c The enthalpy change of formation of CaCl 2 is much more negative than that of CaCl. CaCl 2 has lower energy and is more stable relative to the elements Ca and Cl 2 , and so it is more likely to be formed. 173
SECTION 5 Section 5.1 1 a Ca 2+ (aq) + 2OH – (aq) b Mg 2+ (aq) + SO 2– 4 (aq) c 2Na + (aq) + O 2– (aq) d K + (aq) + OH – (aq) e Ag + (aq) + NO – 3 (aq) f 2Al 3+ (aq) + 3SO 2– 4 (aq) 2 a NaBr b Mg(OH) 2 c Na 2 S d BaO e CaCO 3 f Ca(NO 3 ) 2 g K 2 CO 3 3 a Ba 2+ (aq) + SO 2– 4 (aq) Æ BaSO 4 (s) b Mg 2+ (aq) + 2OH – (aq) Æ Mg(OH) 2 (s) c Ca 2+ (aq) + CO 2– 3 (aq) Æ CaCO 3 (s) d Ba 2+ (aq) + CrO 2– 4 (aq) Æ BaCrO 4 (s) Section 5.2 1 The small size of the carbon atom makes it possible for carbon to form double bonds with oxygen to produce discrete covalent molecules. Silicon, on the other hand, bonds to 4 oxygen atoms to form single bonds and hence a covalent network structure. The attractive forces between the molecules of carbon dioxide (intermolecular forces) are weak so that little energy is needed to separate the individual molecules. Strong covalent bonds exist throughout the SiO 2 covalent network structure so a lot of energy is needed to melt it. 2 a Any attractive forces between the solvent and the atoms in the covalent network structure are too weak to overcome the strong covalent bonds holding the network together. b At room temperature, the kinetic energy of atoms and molecules is small but it may be enough to overcome the weak attractive forces between simple molecules or isolated atoms. 3 a Diamond structure with silicon and carbon atoms alternating. 4 2Na + (aq) + SO 2– 4 (aq) + 10H 2 O(l) Æ Na 2 SO 4 .10H 2 O(s) 5 a H + (aq) + OH – (aq) Æ H 2 O(l) b Zn(s) + 2H + (aq) Æ Zn 2+ (aq) + H 2 (g) c CuO(s) + 2H + (aq) Æ Cu 2+ (aq) + H 2 O(l) d CaCO 3 (s) + 2H + (aq) Æ Ca 2+ (aq) + H 2 O(l) + CO 2 (g) 6 a i Cubic ii Eight iii Eight b The attractions between the oppositely charged caesium and chloride ions greatly outweigh the repulsions between ions with the same charge. The net attractive force is very high. The solid is hard and has a high melting point as this strong attraction has to be overcome to separate the particles. b The silicon and carbon atoms are held together by strong covalent bonds in an extended network structure. This makes the substance very hard. 4 a Graphite structure with alternating boron and nitrogen atoms. b In graphite, each carbon atom has 4 bonding electrons. Only 3 are needed to form the layer structure. The fourth electron is ‘free’ and causes graphite to be a good electrical conductor. Both boron and nitrogen have only 3 bonding electrons. All 3 are needed to form the structure of the layer. There are no electrons available to become delocalised and conduct electricity. 5 It was assumed that buckminsterfullerene was a covalent network structure and would be insoluble like graphite and diamond, but solution in benzene showed it, surprisingly, to be a molecular form of carbon. Attractive forces between the solvent molecules and the carbon atoms are sufficient to overcome the weak intermolecular forces between the buckminsterfullerene molecules. Section 5.3 1 a Kr, Xe (higher b.p.) b C 6 H 14 , C 8 H 18 (higher b.p.) c CH 4 , CCl 4 (higher b.p.) d CH and CH 3 CH 3 CH 3 CH 3 CH 2 CH 2 CH 3 (higher b.p.) 3 pentane e CH 3 methylbutane CH 3 CH CH CH 3 CH 3 and 174 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 (higher b.p.) 2 In the solid or liquid state, noble gas atoms are held together by weak instantaneous dipole–induced dipole forces. It takes very little energy to break these attractions and this results in very low melting and boiling points. dimethylpropane
Page 1 and 2: SECTION 1 Section 1.1 1 a 2.0 b 5.3
Page 3 and 4: SECTION 2 Section 2.2 1 a 238 234 9
Page 5 and 6: SECTION 3 Section 3.2 1 a Li(g) bec
Page 7 and 8: SECTION 3 Section 3.5 1 F F 4 a F 2
Page 9 and 10: SECTION 4 CH 3 CHO(l) +2 O 2 (g)
Page 11: SECTION 4 Section 4.6 1 a i Li(s) +
Page 15 and 16: SECTION 5 5 a H H H c H b H O H C H
Page 17 and 18: SECTION 6 5 a In ionic substances,
Page 19 and 20: SECTION 6 7 Accurate atomic masses
Page 21 and 22: SECTION 7 Section 7.2 1 a 0.09 5 a
Page 23 and 24: SECTION 8 Section 7.7 1 a i AgI(s)
Page 25 and 26: SECTION 9 2 a Buffer solutions are
Page 27 and 28: SECTION 10 Section 10.1 1 a b c A r
Page 29 and 30: SECTION 11 Section 11.2 1 Element T
Page 31 and 32: SECTION 12 Section 11.6 1 a 2 b 4 c
Page 33 and 34: SECTION 12 5 a H H H Br Br + 2Br 2
Page 35 and 36: SECTION 13 6 a H H H H H C C I + OH
Page 37 and 38: SECTION 13 Section 13.4 1 a A butan
Page 39 and 40: SECTION 13 6 a O O CH 3 CH 2 OH + C
Page 41 and 42: SECTION 13 6 a H H OH b H H OH H H
Page 43 and 44: SECTION 14 Section 13.10 1 a + - NH
Page 45 and 46: SECTION 14 5 a i Reagents and condi
Page 47: SECTION 15 Section 15.5 1 a Many of

Section 1.1 Section 1.2 Section 1.3 - The Student Room

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