MCQ
In benzene molecule all $C - C$ bond lengths are equal because
- AAll carbon atoms are equivalent
- BAll carbon atoms are $s{p^2}$ hybridised
- ✓All $C - C$ bonds in benzene, have same order
- DAll $C - C$ bonds are single covalent bond
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$\text{C}(\text{g})+4\text{H}(\text{g})\rightarrow\text{CH}_4(\text{g});\Delta_\text{r}\text{H}=\text{x}\text{kJ}\ \text{mol}^{-1}$
$\text{C}(\text{graphite,s})+2\text{H}_2(\text{g})\rightarrow\text{CH}_4(\text{g});\Delta_\text{r}\text{H}=\text{y}\text{kJ}\ \text{mol}^{-1}$

[Atomic mass: $\mathrm{Ag}=108, \mathrm{Br}=80$ ]
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.