STD 11 - 4. Chemical bonding and molecular structure — NEET STD 11 Science — Question

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The transition temperature for $\alpha$ to $\beta$ phase change is $600 \mathrm{~K}$ and $C_{p, \beta}-C_{p, \alpha}=1 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$. Assume $\left(C_{p, \beta}-C_{p, \alpha}\right)$ is independent of temperature in the range of 200 to $700 \mathrm{~K} . \mathrm{C}_{p, \alpha}$ and $C_{p, \beta}$ are heat capacities of $\alpha$ and $\beta$ phases, respectively.

($1$)The value of entropy change, $\mathrm{S}_\beta-\mathrm{S}_\alpha$ (in $\mathrm{J} \mathrm{mol}^{-1} \mathrm{~K}^{-1}$ ), at $300 \mathrm{~K}$ is. . . . . . .

[Use : $\ln 2=0.69$  Given : $S_\beta-S_\alpha=0$ at $\left.0 \mathrm{~K}\right]$

($2$) The value of enthalpy change, $\mathrm{H}_\beta-\mathrm{H}_\alpha$ (in $J$ mol ${ }^{-1}$ ), at $300 \mathrm{~K}$ is

Give the answer quetion ($1$) and ($2$)

Given : $\Delta H _{ f }^{\ominus}\left( Al _2 O _3\right)=-1700\,kJ\,mol ^{-1}$

$\Delta H _{ f }^\theta\left( Fe _2 O _3\right)=-840\,kJ\,mol ^{-1}$

Molar mass of $Fe , Al$ and $O$ are $56,27$ and $16\,g\,mol ^{-1}$ respectively.