Carbon reacts with oxygen to produce carbon dioxide [tex]\((CO_2(g), \Delta H_f = -393.5 \text{kJ/mol})\)[/tex] according to the equation:

[tex]\[ C(s) + 2O_2(g) \rightarrow CO_2(g) \][/tex]

What is the enthalpy change of the reaction?

A. [tex]\(-393.5 \text{kJ}\)[/tex]
B. [tex]\(-196.8 \text{kJ}\)[/tex]
C. [tex]\(196.8 \text{kJ}\)[/tex]
D. [tex]\(393.5 \text{kJ}\)[/tex]



Answer :

The reaction given is:

[tex]\[ C (s) + O_2 (g) \rightarrow CO_2 (g) \][/tex]

To determine the enthalpy change ([tex]\(\Delta H\)[/tex]) for this reaction, we use the standard enthalpies of formation ([tex]\(\Delta H_f\)[/tex]) of the reactants and products.

The enthalpy change of the reaction can be calculated using:

[tex]\[ \Delta H_{rxn} = \sum (\Delta H_{f, \text{products}}) - \sum (\Delta H_{f, \text{reactants}}) \][/tex]

For this reaction:

- The enthalpy of formation of carbon dioxide ([tex]\( CO_2(g) \)[/tex]) is given as [tex]\(-393.5 \text{ kJ/mol} \)[/tex].
- The standard enthalpy of formation for elemental carbon ([tex]\( C(s) \)[/tex]) and elemental oxygen ([tex]\( O_2(g) \)[/tex]) in their standard states is [tex]\(0 \text{ kJ/mol} \)[/tex].

Thus,

[tex]\[ \sum (\Delta H_{f, \text{products}}) = \Delta H_f (CO_2 (g)) = -393.5 \text{ kJ/mol} \][/tex]

And,

[tex]\[ \sum (\Delta H_{f, \text{reactants}}) = \Delta H_f (C (s)) + \Delta H_f (O_2 (g)) = 0 + 0 = 0 \text{ kJ/mol} \][/tex]

Substituting these values into the equation for [tex]\(\Delta H_{rxn}\)[/tex]:

[tex]\[ \Delta H_{rxn} = (-393.5) - (0) = -393.5 \text{ kJ/mol} \][/tex]

Therefore, the enthalpy change of the reaction is:

[tex]\[ -393.5 \text{ kJ} \][/tex]

So, the enthalpy change of the reaction is [tex]\(-393.5 \text{ kJ} \)[/tex].

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