Answer to Question #159588 in General Chemistry for Isiah

Question

C(s)+H

2

O(g)→CO(g)+H

2

(g)ΔH

°

=+131kJ/mol

rxn

The reaction between C(s)

 and H

2

O(g)

 is represented by the balanced chemical equation above. Based on the enthalpy change of the reaction (ΔH

°

) and the standard heats of formation (ΔH

°

f

) given in the table below, what is the approximate ΔH

°

f

 for CO(g)

 ?

SubstanceΔH

°

f

 (kJ/mol

)C(s)

0H

2

O(g)

−242

CO(g)

?

H

2

(g)

• −373kJ/mol
• negative 373 kilojoules per mole
• A
• −111kJ/mol
• negative 111 kilojoules per mole
• B
• +111kJ/mol
• positive 111 kilojoules per mole
• C
• +373kJ/mol

Answer 1

AnswerFirst write the balanced chemical reactions for the formation of carbon dioxide, carbon monoxide and water.
C+O2​⟶CO2​;ΔH∘=−393.5kJ ... (i)    C+2
1​O2​⟶CO;ΔH∘=−110.5kJ    ...(ii)    
H2​+2
1​O2​⟶H2​O;ΔH∘=−241.8kJ    ...(iii)   Then obtain the required equation by equating (ii)+(iii)−(i):
 CO2​+H2​⟶CO+H2​O;ΔH∘=+41.2     Hence, the standard enthalpy change for the reaction is 41.2 kJ/mol.