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CHM 112
Section 1

Homework Assignment #26
Due April 17, 2006 by 8:05 a.m.

Practice (not to be turned in): 17.41, 17.42

For the reactions corresponding to the fifth digit of your Student ID Number, find Go at 50 °C and at 90 °C. Does the spontaneity increase or decrease as the temperature increases?


Set 0)

Solid strontium chloride reacting with aqueous carbonate ion.

Aqueous nitric acid reacting with solid calcium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 1)

Solid magnesium chloride reacting with aqueous carbonate ion.

Aqueous nitric acid reacting with solid barium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 2)

Solid calcium chloride reacting with aqueous carbonate ion.

Aqueous nitric acid reacting with solid zinc(II) hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 3)

Solid barium chloride reacting with aqueous carbonate ion.

Aqueous nitric acid reacting with solid nickel(II) hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 4)

Solid iron(II) chloride reacting with aqueous carbonate ion.

Aqueous nitric acid reacting with solid magnesium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 5)

Solid silver nitrate reacting with aqueous sulfate ion.

Aqueous sulfuric acid reacting with solid sodium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 6)

Solid silver nitrate reacting with aqueous chloride ion.

Aqueous sulfuric acid reacting with solid potassium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 7)

Solid silver nitrate reacting with aqueous bromide ion.

Aqueous sulfuric acid reacting with aqueous sodium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 8)

Solid silver nitrate reacting with aqueous iodide ion.

Aqueous sulfuric acid reacting with aqueous potassium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.

Set 9)

Solid silver nitrate reacting with aqueous sulfide ion.

Aqueous sulfuric acid reacting with solid lithium hydroxide.

Aqueous bicarbonate ion reacting with aqueous cyanide ion.



Answers:

In all cases, to find G° = H° – TS°, use H° from Homework 24 and S° from Homework 25. T = 50 °C + 273 °C = 323 K, T = 90 °C + 273 °C = 363 K.


Set 0)

SrCl2(s) + CO32–(aq)SrCO3(s) + 2 Cl(aq)

H° = –47 kJ/mole

S° = 150 J/mole·K

G°(323 K) = (–47) – (323)(0.150) = –95. kJ/mole

G°(363 K) = (–47) – (363)(0.150) = –101. kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

2 HNO3(aq) + Ca(OH)2(s)2 H2O(l) + Ca2+(aq) + 2 NO3(aq)

H° = –123.7 kJ/mole

S° = 1.2 J/mole·K

G°(323 K) = (–123.7) – (323)(0.0012) = –124.1 kJ/mole

G°(363 K) = (–123.7) – (363)(0.0012) = –124.1 kJ/mole

Spontaneity is unchanged (G° is the same with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO32–(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 1)

MgCl2(s) + CO32–(aq)MgCO3(s) + 2 Cl(aq)

H° = –112 kJ/mole

S° = 146.0 J/mole·K

G°(323 K) = (–112) – (323)(0.1460) = –159. kJ/mole

G°(363 K) = (–112) – (363)(0.1460) = –165. kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

2 HNO3(aq) + Ba(OH)2(s)2 H2O(l) + Ba2+(aq) + 2 NO3(aq)

H° = –158.4 kJ/mole

S° = 42 J/mole·K

G°(323 K) = (–158.4) – (323)(0.042) = –172.0 kJ/mole

G°(363 K) = (–158.4) – (363)(0.042) = –173.6 kJ/mole

Spontaneity increases slightly (G° is becoming more negative with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO32–(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 2)

CaCl2(s) + CO32–(aq)CaCO3(s) + 2 Cl(aq)

H° = –69 kJ/mole

S° = 154 J/mole·K

G°(323 K) = (–69) – (323)(0.154) = –119. kJ/mole

G°(363 K) = (–69) – (363)(0.154) = –125. kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

2 HNO3(aq) + Zn(OH)2(s)2 H2O(l) + Zn2+(aq) + 2 NO3(aq)

H° = –78.8 kJ/mole

S° = –53.5 J/mole·K

G°(323 K) = (–78.8) – (323)(–0.0535) = –61.5 kJ/mole

G°(363 K) = (–78.8) – (363)(–0.0535) = –59.4 kJ/mole

Spontaneity decreases slightly (G° is becoming more positive with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO32–(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 3)

BaCl2(s) + CO32–(aq)BaCO3(s) + 2 Cl(aq)

H° = –15 kJ/mole

S° = 158 J/mole·K

G°(323 K) = (–15) – (323)(0.158) = –66. kJ/mole

G°(363 K) = (–15) – (363)(0.158) = –72. kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

2 HNO3(aq) + Ni(OH)2(s)2 H2O(l) + Ni2+(aq) + 2 NO3(aq)

H° = –101.1 kJ/mole

S° = –107 J/mole·K

G°(323 K) = (–101.1) – (323)(–0.107) = –66.5 kJ/mole

G°(363 K) = (–101.1) – (363)(–0.107) = –62.3 kJ/mole

Spontaneity decreases slightly (G° is becoming more positive with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO32–(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 4)

FeCl2(s) + CO32–(aq)FeCO3(s) + 2 Cl(aq)

H° = –56.1 kJ/mole

S° = 144.8 J/mole·K

G°(323 K) = (–56.1) – (323)(0.1448) = –102.9 kJ/mole

G°(363 K) = (–56.1) – (363)(0.1448) = –108.7 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

2 HNO3(aq) + Mg(OH)2(s)2 H2O(l) + Mg2+(aq) + 2 NO3(aq)

H° = –109.0 kJ/mole

S° = –61.5 J/mole·K

G°(323 K) = (–109.0) – (323)(–0.0615) = –89.1 kJ/mole

G°(363 K) = (–109.0) – (363)(–0.0615) = –86.7 kJ/mole

Spontaneity decreases slightly (G° is becoming more positive with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO3(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 5)

2 AgNO3(s) + SO42–(aq)Ag2SO4(s) + 2 NO3(aq)

H° = 32.2 kJ/mole

S° = 191.3 J/mole·K

G°(323 K) = (32.2) – (323)(0.1913) = –29.6 kJ/mole

G°(363 K) = (32.2) – (363)(0.1913) = –37.2 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

H2SO4(aq) + 2 NaOH(s)2 H2O(l) + 2 Na+(aq) + SO42–(aq)

H° = –200.6 kJ/mole

S° = 128.9 J/mole·K

G°(323 K) = (–200.6) – (323)(0.1289) = –242.2 kJ/mole

G°(363 K) = (–200.6) – (363)(0.1289) = –247.4 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO3(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 6)

AgNO3(s) + Cl(aq)AgCl(s) + NO3(aq)

H° = –40.5 kJ/mole

S° = 45.2 J/mole·K

G°(323 K) = (–40.5) – (323)(0.0452) = –55.1 kJ/mole

G°(363 K) = (–40.5) – (363)(0.0452) = –56.9 kJ/mole

Spontaneity increases slightly (G° is becoming more negative with increasing temperature)

H2SO4(aq) + 2 KOH(s)2 H2O(l) + 2 K+(aq) + SO42–(aq)

H° = –226.8 kJ/mole

S° = 187.1 J/mole·K

G°(323 K) = (–226.8) – (323)(0.1871) = –287.2 kJ/mole

G°(363 K) = (–226.8) – (363)(0.1871) = –294.7 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO3(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 7)

AgNO3(s) + Br(aq)AgBr(s) + NO3(aq)

H° = –60.1 kJ/mole

S° = 32 J/mole·K

G°(323 K) = (–60.1) – (323)(0.032) = –70.4 kJ/mole

G°(363 K) = (–60.1) – (363)(0.032) = –71.7 kJ/mole

Spontaneity increases slightly (G° is becoming more negative with increasing temperature)

H2SO4(aq) + 2 NaOH(aq)2 H2O(l) + 2 Na+(aq) + SO42–(aq)

H° = –113.4 kJ/mole

S° = 161.6 J/mole·K

G°(323 K) = (–113.4) – (323)(0.1616) = –165.6 kJ/mole

G°(363 K) = (–113.4) – (363)(0.1616) = –172.1 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO3(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 8)

AgNO3(s) + I(aq)AgI(s) + NO3(aq)

H° = –87.3 kJ/mole

S° = 9 J/mole·K

G°(323 K) = (–87.3) – (323)(0.009) = –90.2 kJ/mole

G°(363 K) = (–87.3) – (363)(0.009) = –90.6 kJ/mole

Spontaneity is unchanged, within experimental error (G° is unchanged with increasing temperature)

H2SO4(aq) + 2 KOH(aq)2 H2O(l) + 2 K+(aq) + SO42–(aq)

H° = –111.6 kJ/mole

S° = 161.6 J/mole·K

G°(323 K) = (–111.6) – (323)(0.1616) = –163.8 kJ/mole

G°(363 K) = (–111.6) – (363)(0.1616) = –170.3 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO3(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)


Set 9)

2 AgNO3(s) + S2–(aq)Ag2S(s) + 2 NO3(aq)

H° = –234.8 kJ/mole

S° = 135 J/mole·K

G°(323 K) = (–234.8) – (323)(0.135) = –278.4 kJ/mole

G°(363 K) = (–234.8) – (363)(0.135) = –283.8 kJ/mole

Spontaneity increases (G° is becoming more negative with increasing temperature)

H2SO4(aq) + 2 LiOH(s)2 H2O(l) + 2 Li+(aq) + SO42–(aq)

H° = –158.8 kJ/mole

S° = –13.4 J/mole·K

G°(323 K) = (–158.8) – (323)(–0.0134) = –154.5 kJ/mole

G°(363 K) = (–158.5) – (363)(–0.0134) = –153.9 kJ/mole

Spontaneity is unchanged, within experimental error (G° is unchanged with increasing temperature)

HCO3(aq) + CN(aq)HCN(aq) + CO3(aq)

H° = –32 kJ/mole

S° = –141 J/mole·K

G°(323 K) = (–32) – (323)(–0.141) = 14. kJ/mole

G°(363 K) = (–32) – (363)(–0.141) = 19. kJ/mole

Spontaneity decreases (G° is becoming more positive with increasing temperature)