If the value of $\Delta H$ in a reaction is positive,then the reaction is called

The average $S-F$ bond energy in $kJ \ mol^{-1}$ of $SF_{6}$ is $......$ . (Rounded off to the nearest integer) [Given : The values of standard enthalpy of formation of $SF_{6(g)}$,$S_{(g)}$ and $F_{(g)}$ are $-1100$,$275$ and $80 \ kJ \ mol^{-1}$ respectively.]

The heat of solution of anhydrous $CuSO_4$ and $CuSO_4 \cdot 5 H_2 O$ are $-70 \ kJ \ mol^{-1}$ and $+12 \ kJ \ mol^{-1}$ respectively. The heat of hydration of $CuSO_4$ to $CuSO_4 \cdot 5 H_2 O$ is $-x \ kJ$. The value of $x$ is:

The $\Delta H_f$ for $CO_{2(g)}$,$CO_{(g)}$ and $H_2O_{(g)}$ are $-393.5$,$-110.5$ and $-241.8 \ kJ \ mol^{-1}$ respectively. The standard enthalpy change for the reaction is:
$CO_{2(g)} + H_{2(g)} \to CO_{(g)} + H_2O_{(g)}$

If the standard enthalpies of formation of hydrazine and water are $+50.6 \, kJ/mol$ and $-285.9 \, kJ/mol$ respectively,calculate the $\Delta H$ for the following reaction: $N_2H_{4(g)} + O_{2(g)} \to N_{2(g)} + 2H_2O_{(l)}$ in $kJ \, mol^{-1}$.

Calculate the enthalpy change in $kJ$ for the reaction: $2C_{(graphite)} + 2H_{2(g)} \to C_2H_{4(g)}$
$C_{(graphite)} + O_{2(g)} \to CO_{2(g)} \quad \Delta H = -393.5 \ kJ$
$C_2H_{4(g)} + 3O_{2(g)} \to 2CO_{2(g)} + 2H_2O_{(l)} \quad \Delta H = -1410.9 \ kJ$
$H_{2(g)} + 1/2O_{2(g)} \to H_2O_{(l)} \quad \Delta H = -285.8 \ kJ$