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Chemistry: Atoms First

Chapter 7

Chemistry: Atoms FirstChapter 7

1.

An equation is balanced when the same number of each element is represented on the reactant and product sides. Equations must be balanced to accurately reflect the law of conservation of matter.

3.

(a) PCl5(s)+H2O(l)POCl3(l)+2HCl(aq);PCl5(s)+H2O(l)POCl3(l)+2HCl(aq); (b) 3Cu(s)+8HNO3(aq)3Cu(NO3)2(aq)+4H2O(l)+2NO(g);3Cu(s)+8HNO3(aq)3Cu(NO3)2(aq)+4H2O(l)+2NO(g); (c) H2(g)+I2(s)2HI(s);H2(g)+I2(s)2HI(s); (d) 4Fe(s)+3O2(g)2Fe2O3(s);4Fe(s)+3O2(g)2Fe2O3(s); (e) 2Na(s)+2H2O(l)2NaOH(aq)+H2(g);2Na(s)+2H2O(l)2NaOH(aq)+H2(g); (f) (NH4 )2Cr2O7(s)Cr2O3(s)+N2(g)+4H2O(g);(NH4 )2Cr2O7(s)Cr2O3(s)+N2(g)+4H2O(g); (g) P4(s)+6Cl2(g)4PCl3(l);P4(s)+6Cl2(g)4PCl3(l); (h) PtCl4(s)Pt(s)+2Cl2(g)PtCl4(s)Pt(s)+2Cl2(g)

5.

(a) CaCO3(s)CaO(s)+CO2(g);CaCO3(s)CaO(s)+CO2(g); (b) 2C4H10(g)+13O2(g)8CO2(g)+10H2O(g);2C4H10(g)+13O2(g)8CO2(g)+10H2O(g); (c) MgC12(aq)+2NaOH(aq)Mg(OH)2(s)+2NaCl(aq);MgC12(aq)+2NaOH(aq)Mg(OH)2(s)+2NaCl(aq); (d) 2H2O(g)+2Na(s)2NaOH(s)+H2(g)2H2O(g)+2Na(s)2NaOH(s)+H2(g)

7.

(a) Ba(NO3)2, KClO3; (b) 2KClO3(s)2KCl(s)+3O2(g);2KClO3(s)2KCl(s)+3O2(g); (c) 2Ba(NO3)2(s)2BaO(s)+2N2(g)+5O2(g);2Ba(NO3)2(s)2BaO(s)+2N2(g)+5O2(g); (d) 2Mg(s)+O2(g)2MgO(s);2Mg(s)+O2(g)2MgO(s); 4Al(s)+3O2(g)2Al2O3(s);4Al(s)+3O2(g)2Al2O3(s); 4Fe(s)+3O2(g)2Fe2O3(s)4Fe(s)+3O2(g)2Fe2O3(s)

9.

(a) 4HF(aq)+SiO2(s)SiF4(g)+2H2O(l);4HF(aq)+SiO2(s)SiF4(g)+2H2O(l); (b) complete ionic equation: 2Na+(aq)+2F(aq)+Ca2+(aq)+2Cl(aq)CaF2(s)+2Na+(aq)+2Cl(aq),2Na+(aq)+2F(aq)+Ca2+(aq)+2Cl(aq)CaF2(s)+2Na+(aq)+2Cl(aq), net ionic equation: 2F(aq)+Ca2+(aq)CaF2(s)2F(aq)+Ca2+(aq)CaF2(s)

11.

(a) 2K+(aq)+C2O42−(aq)+Ba2+(aq)+2OH(aq)2K+(aq)+2OH(aq)+BaC2O4(s)(complete)Ba2+(aq)+C2O42−(aq)BaC2O4(s)(net)2K+(aq)+C2O42−(aq)+Ba2+(aq)+2OH(aq)2K+(aq)+2OH(aq)+BaC2O4(s)(complete)Ba2+(aq)+C2O42−(aq)BaC2O4(s)(net)
(b) Pb2+(aq)+2NO3(aq)+2H+(aq)+SO42−(aq)PbSO4(s)+2H+(aq)+2NO3(aq)(complete)Pb2+(aq)+SO42−(aq)PbSO4(s)(net)Pb2+(aq)+2NO3(aq)+2H+(aq)+SO42−(aq)PbSO4(s)+2H+(aq)+2NO3(aq)(complete)Pb2+(aq)+SO42−(aq)PbSO4(s)(net)
(c) CaCO3(s)+2H+(aq)+SO42−(aq)CaSO4(s)+CO2(g)+H2O(l)(complete)CaCO3(s)+2H+(aq)+SO42−(aq)CaSO4(s)+CO2(g)+H2O(l)(net)CaCO3(s)+2H+(aq)+SO42−(aq)CaSO4(s)+CO2(g)+H2O(l)(complete)CaCO3(s)+2H+(aq)+SO42−(aq)CaSO4(s)+CO2(g)+H2O(l)(net)

13.

(a) oxidation-reduction (addition); (b) acid-base (neutralization); (c) oxidation-reduction (combustion)

15.

It is an oxidation-reduction reaction because the oxidation state of the silver changes during the reaction.

17.

(a) H +1, P +5, O −2; (b) Al +3, H +1, O −2; (c) Se +4, O −2; (d) K +1, N +3, O −2; (e) In +3, S −2; (f) P +3, O −2

19.

(a) acid-base; (b) oxidation-reduction: Na is oxidized, H+ is reduced; (c) oxidation-reduction: Mg is oxidized, Cl2 is reduced; (d) acid-base; (e) oxidation-reduction: P3− is oxidized, O2 is reduced; (f) acid-base

21.

(a) 2HCl(g)+Ca(OH)2(s)CaCl2(s)+2H2O(l);2HCl(g)+Ca(OH)2(s)CaCl2(s)+2H2O(l); (b) Sr(OH)2(aq)+2HNO3(aq)Sr(NO3)2(aq)+2H2O(l)Sr(OH)2(aq)+2HNO3(aq)Sr(NO3)2(aq)+2H2O(l)

23.

(a) 2Al(s)+3F2(g)2AlF3(s);2Al(s)+3F2(g)2AlF3(s); (b) 2Al(s)+3CuBr2(aq)3Cu(s)+2AlBr3(aq);2Al(s)+3CuBr2(aq)3Cu(s)+2AlBr3(aq); (c) P4(s)+5O2(g)P4O10(s);P4(s)+5O2(g)P4O10(s); (d) Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

25.

(a) Mg(OH)2(s)+2HClO4(aq)Mg2+(aq)+2ClO4(aq)+2H2O(l);Mg(OH)2(s)+2HClO4(aq)Mg2+(aq)+2ClO4(aq)+2H2O(l); (b) SO3(g)+2H2O(l)H3O+(aq)+HSO4(aq),SO3(g)+2H2O(l)H3O+(aq)+HSO4(aq), (a solution of H2SO4); (c) SrO(s)+H2SO4(l)SrSO4(s)+H2OSrO(s)+H2SO4(l)SrSO4(s)+H2O

27.

H 2 ( g ) + F 2 ( g ) 2HF ( g ) H 2 ( g ) + F 2 ( g ) 2HF ( g )

29.

2NaBr ( a q ) + Cl 2 ( g ) 2 NaCl ( a q ) + Br 2 ( l ) 2NaBr ( a q ) + Cl 2 ( g ) 2 NaCl ( a q ) + Br 2 ( l )

31.

2 LiOH ( a q ) + CO 2 ( g ) Li 2 CO 3 ( a q ) + H 2 O ( l ) 2 LiOH ( a q ) + CO 2 ( g ) Li 2 CO 3 ( a q ) + H 2 O ( l )

33.

(a) Ca(OH)2(s)+H2S(g)CaS(s)+2H2O(l);Ca(OH)2(s)+H2S(g)CaS(s)+2H2O(l); (b) Na2CO3(aq)+H2S(g)Na2S(aq)+CO2(g)+H2O(l)Na2CO3(aq)+H2S(g)Na2S(aq)+CO2(g)+H2O(l)

35.

(a) step 1: N2(g)+3H2(g)2NH3(g),N2(g)+3H2(g)2NH3(g), step 2: NH3(g)+HNO3(aq)NH4NO3(aq)NH4NO3(s)(after drying);NH3(g)+HNO3(aq)NH4NO3(aq)NH4NO3(s)(after drying); (b) H2(g)+Br2(l)2HBr(g);H2(g)+Br2(l)2HBr(g); (c) Zn(s)+S(s)ZnS(s)Zn(s)+S(s)ZnS(s) and ZnS(s)+2HCl(aq)ZnCl2(aq)+H2S(g)ZnS(s)+2HCl(aq)ZnCl2(aq)+H2S(g)

37.

(a) Sn4+(aq)+2eSn2+(aq),Sn4+(aq)+2eSn2+(aq), (b) [Ag(NH3)2]+(aq)+eAg(s)+2NH3(aq);[Ag(NH3)2]+(aq)+eAg(s)+2NH3(aq); (c) Hg2Cl2(s)+2e2Hg(l)+2Cl(aq);Hg2Cl2(s)+2e2Hg(l)+2Cl(aq); (d) 2H2O(l)O2(g)+4H+(aq)+4e;2H2O(l)O2(g)+4H+(aq)+4e; (e) 6H2O(l)+2IO3(aq)+10eI2(s)+12OH(aq);6H2O(l)+2IO3(aq)+10eI2(s)+12OH(aq); (f) H2O(l)+SO32−(aq)SO42−(aq)+2H+(aq)+2e;H2O(l)+SO32−(aq)SO42−(aq)+2H+(aq)+2e; (g) 8H+(aq)+MnO4(aq)+5eMn2+(aq)+4H2O(l);8H+(aq)+MnO4(aq)+5eMn2+(aq)+4H2O(l); (h) Cl(aq)+6OH(aq)ClO3(aq)+3H2O(l)+6eCl(aq)+6OH(aq)ClO3(aq)+3H2O(l)+6e

39.

(a) Sn2+(aq)+2Cu2+(aq)Sn4+(aq)+2Cu+(aq);Sn2+(aq)+2Cu2+(aq)Sn4+(aq)+2Cu+(aq); (b) H2S(g)+Hg22+(aq)+2H2O(l)2Hg(l)+S(s)+2H3O+(aq);H2S(g)+Hg22+(aq)+2H2O(l)2Hg(l)+S(s)+2H3O+(aq); (c) 5CN(aq)+2ClO2(aq)+3H2O(l)5CNO(aq)+2Cl(aq)+2H3O+(aq);5CN(aq)+2ClO2(aq)+3H2O(l)5CNO(aq)+2Cl(aq)+2H3O+(aq); (d) Fe2+(aq)+Ce4+(aq)Fe3+(aq)+Ce3+(aq);Fe2+(aq)+Ce4+(aq)Fe3+(aq)+Ce3+(aq); (e) 2HBrO(aq)+2H2O(l)2H3O+(aq)+2Br(aq)+O2(g)2HBrO(aq)+2H2O(l)2H3O+(aq)+2Br(aq)+O2(g)

41.

(a) 2MnO4(aq)+3NO2(aq)+H2O(l)2MnO2(s)+3NO3(aq)+2OH(aq);2MnO4(aq)+3NO2(aq)+H2O(l)2MnO2(s)+3NO3(aq)+2OH(aq); (b) 3MnO42−(aq)+2H2O(l)2MnO4(aq)+4OH(aq)+MnO2(s)(in base);3MnO42−(aq)+2H2O(l)2MnO4(aq)+4OH(aq)+MnO2(s)(in base); (c) Br2(l)+SO2(g)+2H2O(l)4H+(aq)+2Br(aq)+SO42−(aq)Br2(l)+SO2(g)+2H2O(l)4H+(aq)+2Br(aq)+SO42−(aq)

43.

(a) 0.435 mol Na, 0.217 mol Cl2, 15.4 g Cl2; (b) 0.005780 mol HgO, 2.890 ×× 10−3 mol O2, 9.248 ×× 10−2 g O2; (c) 8.00 mol NaNO3, 6.8 ×× 102 g NaNO3; (d) 1665 mol CO2, 73.3 kg CO2; (e) 18.86 mol CuO, 2.330 kg CuCO3; (f) 0.4580 mol C2H4Br2, 86.05 g C2H4Br2

45.

(a) 0.0686 mol Mg, 1.67 g Mg; (b) 2.701 ×× 10−3 mol O2, 0.08644 g O2; (c) 6.43 mol MgCO3, 542 g MgCO3 (d) 713 mol H2O, 12.8 kg H2O; (e) 16.31 mol BaO2, 2762 g BaO2; (f) 0.207 mol C2H4, 5.81 g C2H4

47.

(a) volume HCl solutionmol HClmol GaCl3;volume HCl solutionmol HClmol GaCl3; (b) 1.25 mol GaCl3, 2.2 ×× 102 g GaCl3

49.

(a) 5.337 ×× 1022 molecules; (b) 10.41 g Zn(CN)2

51.

SiO2+3CSiC+2CO,SiO2+3CSiC+2CO, 4.50 kg SiO2

53.

5.00 ×× 103 kg

55.

1.28 ×× 105 g CO2

57.

161.40 mL KI solution

59.

176 g TiO2

61.

The limiting reactant is Cl2.

63.

Percent yield=31%Percent yield=31%

65.

gCCl4molCCl4molCCl2F2gCCl2F2,gCCl4molCCl4molCCl2F2gCCl2F2, percent yield=48.3%percent yield=48.3%

67.

percent yield = 91.3% percent yield = 91.3%

69.

Convert mass of ethanol to moles of ethanol; relate the moles of ethanol to the moles of ether produced using the stoichiometry of the balanced equation. Convert moles of ether to grams; divide the actual grams of ether (determined through the density) by the theoretical mass to determine the percent yield; 87.6%

71.

The conversion needed is mol CrmolH3PO4.mol CrmolH3PO4. Then compare the amount of Cr to the amount of acid present. Cr is the limiting reactant.

73.

Na2C2O4 is the limiting reactant. percent yield = 86.6%

75.

Only four molecules can be made.

77.

This amount cannot be weighted by ordinary balances and is worthless.

79.

3.4 ×× 10−3 M H2SO4

81.

9.6 ×× 10−3 M Cl

83.

22.4%

85.

The empirical formula is BH3. The molecular formula is B2H6.

87.

49.6 mL

89.

13.64 mL

91.

0.0122 M

93.

34.99 mL KOH

95.

The empirical formula is WCl4.

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