Paper 1 October/November 2007 CHEMISTRY (9701/01) IGCSE

Calcium carbide, $Ca{C_2}$, reacts with water, as shown. The data below the equation show, in $kJmo{l^{-1}},$ the standard enthalpies of formation of the compounds involved.
$\eqalign{
& Ca{C_2}\left( s \right) + {H_2}O\left( l \right) \to CaO\left( s \right) + {C_2}{H_2}\left( g \right) \cr
& \,\,-60{\text{ }}\,\,\,\,\,\,\,\,\,\,-286{\text{ }}\,\,\,\,\,\,\,\,\,\,\,-635{\text{ }}\,\,\,\,\,\,\,{\text{ }} + 228 \cr} $
What is the standard…