When 0.250 mol of CH₄(g) reacts with excess Cl₂(g) at constant pressure according to the chemical equation shown below, 177 kJ of heat are released. Calculate the value of ?H for this reaction, as written.
2 CH4(g) + 3 Cl₂(g) ? 2 CHCl₃(l) + 3 H₂(g) ?H = ?
O -708 kJ
O +708 kJ
O -1420 kJ
O +1420 kJ