${\mathrm{CO}}_{(\mathrm{g})}+{\mathrm{H}}_2{\mathrm{O}}_{(\mathrm{g})}ightarrow{\mathrm{CO}}_{2(\mathrm{g})}+{\mathrm{H}}_{2(\mathrm{g})}$ Calculate the standard heat change of the reaction above if the standard enthalpies of formation of ${\mathrm{CO}}_{2(g)},{\mathrm{H}}_2{\mathrm{O}}_{(g)}$ and ${\mathrm{CO}}_{(\mathrm{g})}$ in ${\mathrm{KJmol}}^{-1}$ are $-394,-242$ and $-110$ respectively.

A. $+262\mathrm{KJ}{\mathrm{mol}}^{-1}$
B. $-262\mathrm{KJ}\mathrm{mol}{\mathrm{m}}^{-1}$
C. $+42\mathrm{KJ}{\mathrm{mol}}^{-1}$
D. $-42\mathrm{KJ}{\mathrm{mol}}^{-1}$  

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Correct Answer: D