Given the following thermochemical equations:
$(i) \ Zn + \frac{1}{2}O_2 \rightarrow ZnO + 84000 \ cal$
$(ii) \ Hg + \frac{1}{2}O_2 \rightarrow HgO + 21700 \ cal$
Calculate the heat of reaction $(\Delta H)$ for the reaction: $Zn + HgO \rightarrow ZnO + Hg$. (in $cal$)

The heat change for the following reaction $C_{(s)} + 2S_{(s)} \to CS_{2(l)}$ is known as

The reaction of methanol $(\Delta H_f^o = -238.7 \ kJ \ mol^{-1})$ with $2$-methylpropene produces methyl tert-butyl ether $(\Delta H_f^o = -313.6 \ kJ \ mol^{-1})$. Given the reaction: $(CH_3)_2C = CH_2 + CH_3OH \rightarrow (CH_3)_3C - OCH_3; \Delta H^o = -57.8 \ kJ \ mol^{-1}$,calculate the $\Delta H_f^o$ for $2$-methylpropene.

$2C + O_2 \to 2CO$; $\Delta H = -220 \ kJ$. Which of the following statements is correct for this reaction?

Given the following thermochemical equations:
$1) \ C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)}, \Delta H = -787 \ kJ$
$2) \ H_{2(g)} + \frac{1}{2} O_{2(g)} \rightarrow H_2O_{(l)}, \Delta H = -286 \ kJ$
$3) \ C_2H_{2(g)} + \frac{5}{2} O_{2(g)} \rightarrow 2CO_{2(g)} + H_2O_{(l)}, \Delta H = -1310 \ kJ$
Calculate the enthalpy of formation of acetylene $(C_2H_{2(g)})$ in $kJ \ mol^{-1}$.

For the reaction $H_{2(g)} + I_{2(g)} \rightarrow 2HI_{(g)}; \Delta H = 12.40 \, Kcal$,the heat of formation of $HI$ is ....... $Kcal$.