Question

Given that,
$2 C _{(s)}+2 O _{2(g)} \rightarrow 2 CO _{2(g)} ; \Delta H=-787 \,kJ$
$H _{2(g)}+\frac{1}{2} O _{2(g)} \rightarrow H _{2} O _{(l)} ; \Delta H=-286\, kJ$
$C _{2} H _{2(g)}+\frac{5}{2} O _{2(g)} \rightarrow 2 CO _{2(g)}+ H _{2} O _{(l)} ; \Delta H=-1301\, kJ$
Heat of formation of acetylene is

• A. $-1802\, kJ$
• B. $+1802\, kJ$
• C. $-800\, kJ$
• D. $+228\, kJ$

Answer 1

Answer: (D)

Aim :$2 C _{(s)}+ H _{2(g)} \rightarrow C _{2} H _{2(g)}$

Operate (i) $+( ii )-( iii ),$ we get

$\Delta H=-787+(-286)-(-1301)=+228\, kJ$