Answer
15700 kJ
Work Step by Step
Moles of $NO_{2}=\frac{mass\,in\,grams}{molar\,mass\,of\,NO_{2}}$
$=\frac{1.26\times10^{4}\,g}{46.0\,g/mol}=274\,mol$
When 2 moles of $NO_{2}$ are produced, heat given off is 114.6 kJ. This implies that the heat given off per mole $NO_{2}$ produced is 57.3 kJ.
Heat given off when 274 mol of $NO_{2}$ are produced=
$274\,mol\times57.3\,kJ/mol=15700\,kJ$
