Three thermochemical equations are given below:
$(i) C_{(graphite)} + O_{2(g)} \to CO_{2(g)}; \Delta_r H^\circ = x \ kJ \ mol^{-1}$
$(ii) C_{(graphite)} + \frac{1}{2} O_{2(g)} \to CO_{(g)}; \Delta_r H^\circ = y \ kJ \ mol^{-1}$
$(iii) CO_{(g)} + \frac{1}{2} O_{2(g)} \to CO_{2(g)}; \Delta_r H^\circ = z \ kJ \ mol^{-1}$
Based on the above equations,find out which of the relationship given below is correct.

The enthalpy of solution of $BaCl_{2(s)}$ and $BaCl_2 \cdot 2H_2O_{(s)}$ are $-20.6 \, kJ \, mol^{-1}$ and $8.8 \, kJ \, mol^{-1}$ respectively. The enthalpy change for the reaction $BaCl_{2(s)} + 2H_2O_{(l)} \to BaCl_2 \cdot 2H_2O_{(s)}$ is $...... \, kJ \, mol^{-1}$.

When ethyne is passed through a red hot tube,the formation of benzene takes place :-
$\Delta H_{f(C_2H_2)(g)}^o = 230 \ kJ \ mol^{-1}$
$\Delta H_{f(C_6H_6)(g)}^o = 85 \ kJ \ mol^{-1}$
Calculate the standard heat of trimerisation of ethyne to benzene.
$3C_2H_{2(g)} \to C_6H_{6(g)}$
......$kJ \ mol^{-1}$

The atomization enthalpies of $NH_{3(g)}$ and $N_2H_{4(g)}$ are $+150 \ kJ \ mol^{-1}$ and $+310 \ kJ \ mol^{-1}$ respectively. The $\Delta H(N-N)$ bond enthalpy in $kJ \ mol^{-1}$ is:

If the enthalpies of formation of $Al_2O_3$ and $Cr_2O_3$ are $-1596 \, kJ/mol$ and $-1134 \, kJ/mol$ respectively,then calculate $\Delta H$ for the following reaction in $kJ$:
$2Al + Cr_2O_3 \to Al_2O_3 + 2Cr$

The heats of hydrogenation for $3-$-methylbutene and $2-$-pentene are $-30\, kcal/mol$ and $-28\, kcal/mol$ respectively. The heats of combustion of $2-$-methylbutane and pentane are $-784\, kcal/mol$ and $-782\, kcal/mol$ respectively. All the values are given under standard conditions. Taking into account that combustion of both alkanes gives the same products,what is $\Delta H$ (in $kcal/mol$) for the following reaction under same conditions?
$3-$-methylbutene $\rightleftharpoons$ $2-$-pentene