1. Using the enthalpies of formation given below, calculate H° rxn in kJ, for th

Question

1. Using the enthalpies of formation given below, calculate H°rxn in kJ, for the following reaction.

Report your answer to two decimal places in standard notation.



2H2S(g) + 3O2(g) 2SO2(g) + 2H2O(l)



H2S (g): -20.60 kJ/mol

O2 (g): 0.00 kJ/mol

SO2 (g): -296.84 kJ/mol

H2O (l): -285.83 kJ/mol

2-Calculate the amount of heat absorbed/released (in kJ) when 2.64 grams of SO2 are produced via the above reaction.

Report your answer to two decimal places, and use appropriate signs to indicate heat flow direction.

Explanation / Answer

1)

H°rxn = H° products - H° reactants

= (2 x -296.84 + 2 x -285.83) - (2 x -20.60 + 3 x0)

= -1165.34 + 41.20

= -1124.14 kJ/mol

H°rxn = -1124.14 kJ/mol

2)

2H2S(g) + 3O2(g) -------------> 2SO2(g) + 2H2O(l)

2 x 64

moles of SO2 = 2.64 / 64 = 0.04125

for 2 mol SO2 ----------------------> -1124.14 kJ

0.04125 mol SO2--------------------> x kJ

x = -1124.14 x 0.04125 / 2

x = - 23.185 kJ

amount of heat released =  - 23.18 kJ

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