Answer
$\Delta H = 210 kJ$
Work Step by Step
Looking at the coefficients of the thermochemical equation, we see that the formation of 3 moles of acetylene (C2H2) leads to a $\Delta H = 630 kJ $.
Therefore, to find the $\Delta H$ of one mole, we divide this number by 3:
$\Delta H = 630kJ/3 = 210 kJ $
