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Section 3: Thermochemical Equations

Thermochemical Equations

1.
How much heat is evolved when 27.0 g of glucose is burned according to this equation?
C6H12O6 + 6O2 → 6CO2 + 6H2O; Δ H comb. = -2808kJ

Specific Heats of Common Substances at 298 K (25°C)
Substance
Specific heat
J/(g·°C)
Water(l)
(liquid)
4.184
Water(s)
(ice)
2.03
Water(g)
(steam)
2.01
Ethanol(l)
(grain alcohol)
2.44
Aluminum(s)
0.897
Granite(s)
0.803
Iron(s)
0.449
Lead(s)
0.129
Silver(s)
0.235
Gold(s)
0.129


A)136 kJ
B)280 kJ
C)421 kJ
D)421 J
2.
How much heat is required to melt 200 grams of ice? The heat of fusion is 333 J/g.
A)66.6 kJ
B)666 J
C)1.66 J
D)6.66 kJ
3.
Calculate the amount of heat absorbed by 10.0 grams of ice at -15.0°C as it is converted to liquid water at 50.0°C. The specific heat of H2O(s) = 2.09 J/(g·°C). The specific heat of H2O(l) = 4.18 J/(g·°C). The heat of fusion is 333 J/g.
A)5.73 kJ
B)0.676 kJ
C)0.170 kJ
D)2.83 kJ
4.
From the following data,
H2 (g) + Cl2 (g) → 2HCl(g) ΔH°v = -185 kJ
2H2 (g) + O2 (g) → 2H2O(g) ΔH° = -483.7 kJ
calculate ΔH° for the following reaction.
4HCl(g) + O2 (g) → 2Cl2 (g) + 2H2O(g)
A)299 kJ
B)-114 kJ
C)-299 kJ
D)114 kJ
5.
Given the following information,
SO3 (g) + H2O(l) → H2SO4 (l) ΔH° = -133 kJ
Pb(s) + PbO2 (s) + 2H2SO4(l) → 2PbSO4(s) + 2H2O(l) ΔH° = -509 kJ
calculate the ΔH° for the reaction below.
Pb(s) + PbO2 (s) + 2SO3 (g) → 2PbSO4 (s)
A)376 kJ
B)-376 kJ
C)-642 kJ
D)-775 kJ
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