Model Paper 2 — Chemistry STD 11 Science — Question

1.  Throwing a stone from the ground to roof.
2.  $\frac{1}{2}\text{H}_2(\text{g})+\frac{1}{2}\text{Cl}_2(\text{g})\rightleftharpoons\text{HCl}(\text{g})$ $\Delta_\text{r}\text{H}^\ominus=-92.32\text{kJ}\ \text{mol}^{-1}$​​​​​​

$\text{CH}_3\text{OH}(\text{I})+\frac{3}{2}\text{O}_2(\text{g})\xrightarrow{\ \ \ \ \ \ }\text{CO}_2(\text{g})+2\text{H}_2\text{O}(\text{I});\Delta_{\text{r}}\text{H}^\ominus=-726\text{kJ} \ \text{mol}^{-1}$

$\text{C}(\text{graphite})+\text{O}_{2(\text{g})}\xrightarrow{\ \ \ \ \ \ }\text{CO}_{2(\text{g})};\Delta_{\text{c}}\text{H}^\ominus=-393\text{kJ} \ \text{mol}^{-1}$

$\text{H}_2(\text{g})+\frac{1}{2}\text{O}_{2(\text{g})}\xrightarrow{\ \ \ \ \ \ }\text{H}_2\text{O}(\text{I});\Delta_{\text{f}}\text{H}^\ominus=-286\text{kJ} \ \text{mol}^{-1}$.

1. Derive the mathematical expression for first law of thermodynamics.
2. Calculate the $\Delta_\text{r}\text{H}^\circ$ for the reaction:

H₂(g) + Br₂(g) → 2HBr(g)

Bond enthalpy are given as, H-H = 436kJ mol^-1, Br-Br = 192kJ mol^-1 and H-Br = 368kJ mol^-1