Factors Affecting the Value of Keq: Temperature Compound Hof (in kJ/mol) Compoun

Question

Factors Affecting the Value of Keq: Temperature
Compound   Hof (in kJ/mol)   Compound   Hof (in kJ/mol)
HI (g)   26.48
Ca2+ (aq)
-542.83
CO32- (aq)   -677.14
CO2 (g)   -393.5
H2CO3 (aq)   -699.65
H2O (g)   -241.8
H+ (aq)   0.00
CO (g)   -110.5
N2O4 (g)   11.1
SO2 (g)   -296.8
NO2 (g)   33.2
SO3 (g)   -395.7
CaCO3 (s)   -1206.9

Which of the following equilibria will shift toward the products when heated? Check all that apply.

2 SO2(g) + O2(g) equilibrium reaction arrow 2 SO3(g)
H2(g) + CO2(g) equilibrium reaction arrow H2O(g) + CO(g)
2HI(g) equilibrium reaction arrow I2(s) + H2(g)
CaCO3(s) equilibrium reaction arrow Ca2+(aq) + CO32-(aq)
N2O4(g) equilibrium reaction arrow 2 NO2(g)
2 H+(aq) + CO32-(aq) equilibrium reaction arrow H2CO3(aq

Explanation / Answer

1. 2SO2(g) + O2(g) 2SO3(g)

H° = 2 sum of H°SO3(g) - [2 sum of H°SO2(g) + sum of H°O2(g)] =  -197.8 kJ/mol

This shows a negative H° so it will shift towards the products when heated.

2. H2(g) + CO2(g) H2O(g) + CO(g)

H° = -241.8 -110.5 - 0 + 393.5 = 41.2 kJ/mol

This shows a positive H° so it will shift towards the reactant side when heated.

3. 2HI (g) I2(s) + H2(g)

H° = 0 -26.48 = - 26.48 kJ/mol

   This shows a negative H° so it will shift towards the products when heated.

4. CaCO3(s) Ca2+(aq) + CO32-(aq)

H° = -542.83 - 677.14 - (-1206.9) = -13.07 kJ/mol

This shows a negative H° so it will shift towards the products when heated.

5. N2O4(g) 2 NO2 (g)

H° = 33.2 x 2 - 11.1 = 55.3 kJ/mol

This shows a positive H° so it will shift towards the reactant side when heated.

6. 2H+(aq) + CO32- H2CO3(aq)

H° = -699.65 - 2 x 0 - 677.14 = -1376.79 kJ/mol

This shows a negative H° so it will shift towards the products when heated.

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