Embibe Experts Solutions for Chapter: Thermodynamics & Thermochemistry, Exercise 1: EXERCISE

The heat of formation of ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)$ is $-66 \mathrm{kcal}/\mathrm{mole}$. The heat of combustion of ${\mathrm{CH}}_3{\mathrm{OCH}}_3\left(\mathrm{g}\right)$ is $-348 \mathrm{kcal}/\mathrm{mole}. ∆{\mathrm{H}}_{\mathrm{f}}$ for ${\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{CO}}_2$ are $-68 \mathrm{kcal}/\mathrm{mole}$ and $-94 \mathrm{kcal}/\mathrm{mole}$ respectively. Then determine the $\mathrm{\Delta H}$ for the isomerisation reaction ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)⟶{\mathrm{CH}}_3{\mathrm{OCH}}_3\left(\mathrm{g}\right)$, and $\mathrm{\Delta E}$ for the same are at $\mathrm{T}=25°\mathrm{C}$.

In the reaction, ${\mathrm{AB}}_2\left(\mathrm{l}\right)+3{\mathrm{X}}_2\left(\mathrm{g}\right)\rightleftharpoons {\mathrm{AX}}_2\left(\mathrm{g}\right)+2{\mathrm{BX}}_2\left(\mathrm{g}\right) \mathrm{\Delta H}=-270 \mathrm{kcal} \mathrm{per} \mathrm{mol}$ of ${\mathrm{AB}}_2\left(\mathrm{l}\right)$, the enthalpies of formation of ${\mathrm{AX}}_2\left(\mathrm{g}\right) \& {\mathrm{BX}}_2\left(\mathrm{g}\right)$ are in the ratio of $4:3$ and have opposite sign. Determine the value of ${\mathrm{\Delta H}}_{\mathrm{f}}^0\left({\mathrm{AB}}_2\left(\mathrm{l}\right)\right)=+30 \mathrm{Kcal}/\mathrm{mole}$.

$\mathrm{AB}, {\mathrm{A}}_2$ and ${\mathrm{B}}_2$ are diatomic molecules. If the bond enthalpies of ${\mathrm{A}}_2, \mathrm{AB} \& {\mathrm{B}}_2$ are in the ratio $1:1:0.5$ and enthalpy of formation of $\mathrm{AB}$ from ${\mathrm{A}}_2$ and ${\mathrm{B}}_2$ is $-100 \mathrm{kJ}/{\mathrm{mol}}^{-1}$. What is the bond enthalpy of ${\mathrm{A}}_2$?

When a certain amount of ethylene was combusted, $6226 \mathrm{kJ}$ heat was evolved. If heat of combustion of ethylene is$1411 \mathrm{kJ}$, determine the volume of ${\mathrm{O}}_2$ (at $\mathrm{NTP}$) that entered into the reaction.

Given the following reactions:

I: ${\mathrm{N}}_2\left(\mathrm{g}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)⟶2{\mathrm{NO}}_2\left(\mathrm{g}\right), {\mathrm{\Delta H}}_{\mathrm{I}}=16.18 \mathrm{kcal}$

II: ${\mathrm{N}}_2\left(\mathrm{g}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)⟶{\mathrm{N}}_2{\mathrm{O}}_4\left(\mathrm{g}\right), {\mathrm{\Delta H}}_{\mathrm{II}}=2.31 \mathrm{kcal}$

Which amongst ${\mathrm{NO}}_2\left(\mathrm{g}\right)$ and ${\mathrm{N}}_2{\mathrm{O}}_4\left(\mathrm{g}\right)$ is more stable?

Enthalpy of polymerisation of ethylene, as represented by the reaction, ${\mathrm{nCH}}_2={\mathrm{CH}}_2⟶{\left(-{\mathrm{CH}}_2-{\mathrm{CH}}_2-\right)}_{\mathrm{n}}$ is $-100 \mathrm{kJ}$ per mole of ethylene. Given bond enthalpy of $\mathrm{C}=\mathrm{C}$ bond is $600 \mathrm{kJ} {\mathrm{mol}}^{-1}$, determine enthalpy of $\mathrm{C}-\mathrm{C}$ bond (in $\mathrm{kJ} \mathrm{mol}$).

Substance ${\mathrm{A}}_2\mathrm{B}\left(\mathrm{g}\right)$ can undergo decomposition to form two sets of products:

If the molar ratio of ${\mathrm{A}}_2\left(\mathrm{g}\right)$ to $\mathrm{A}\left(\mathrm{g}\right)$ is $5:3$ in a set of product gases, determine then the energy involved in the decomposition of $1$mole of ${\mathrm{A}}_2\mathrm{B}$.

For the hypothetical reaction:

${\mathrm{A}}_2\left(\mathrm{g}\right)+{\mathrm{B}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{AB}\left(\mathrm{g}\right)$

If ${\mathrm{\Delta }}_{\mathrm{r}}{\mathrm{G}}^{\underset{-}{\mathrm{o}}}$ and ${\mathrm{\Delta }}_{\mathrm{r}}{\mathrm{S}}^{\underset{-}{\mathrm{o}}}$ are $20 \mathrm{kJ}/\mathrm{mol}$ and $-20 {\mathrm{JK}}^{-1} {\mathrm{mol}}^{-1}$, respectively at $200 \mathrm{K}. {\mathrm{\Delta }}_{\mathrm{r}}{\mathrm{C}}_{\mathrm{p}}$ is $20 {\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}$ then determine ${\mathrm{\Delta }}_{\mathrm{r}}\mathrm{H}°$ at $400 \mathrm{K}$.