Calculate the change in enthalpy when $39 \ g$ of acetylene is completely burnt with oxygen,given that the enthalpy of combustion of acetylene is $1300 \ kJ \ mol^{-1}$. (in $kJ$)

Using the given reaction enthalpies,find the enthalpy of formation of $H_2O_2(l)$ in $kJ/mol$.
$(i) N_2H_4(l) + 2H_2O_2(l) \rightarrow N_2(g) + 4H_2O(l); \Delta_r H_1^\circ = -818 \, kJ/mol$
$(ii) N_2H_4(l) + O_2(g) \rightarrow N_2(g) + 2H_2O(l); \Delta_r H_2^\circ = -622 \, kJ/mol$
$(iii) H_2(g) + \frac{1}{2} O_2(g) \rightarrow H_2O(l); \Delta_r H_3^\circ = -285 \, kJ/mol$

Given that $C + O_{2} \longrightarrow CO_{2} ; \Delta H^{\circ} = -x \ kJ$ and $2 CO + O_{2} \longrightarrow 2 CO_{2} ; \Delta H^{\circ} = -y \ kJ$. The heat of formation of carbon monoxide will be

At $298 \, K$,the bond energies of $C-H$,$C-C$,$C=C$,and $H-H$ bonds are $414$,$347$,$615$,and $435 \, kJ \, mol^{-1}$ respectively. What is the enthalpy change for the reaction $H_2C=CH_{2(g)} + H_{2(g)} \rightarrow H_3C-CH_{3(g)}$ at $298 \, K$?

For the reaction $C_{2}H_{6} \rightarrow C_{2}H_{4} + H_{2}$,the reaction enthalpy $\Delta_{r}H = \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \, kJ \, mol^{-1}$. (Round off to the Nearest Integer). [Given: Bond enthalpies in $kJ \, mol^{-1} : C-C : 347, C=C : 611, C-H : 414, H-H : 436$]

Given the thermochemical equation,$2 H_{2(g)} + O_{2(g)} \rightarrow 2 H_2O_{(l)}$; $\Delta H = -571.6 \ kJ$. The heat of decomposition of water is: