- ✓Metals
- BNon-metals
- CMetalloids
- DNone of these
Among these elements, metals are in the maximum number. There are $95$ metals and seventeen non-metals. Rest are metalloids such as Silicon, Arsenic, Boron, etc.
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$E^o (Fe^{+2}, Fe) = -0.44$ $ V$
$E^o (Zn^{+2}, Zn) = -0.76$ $ V$
$E^o (Cu^{+2}, Cu) = +0.34$ $V$
$E^o (Cr^{+2}, Cr) = -0.74$ $V$
$E^o (H^+, 1/2H_2) = -0.00$ $V$
$C_{(graphite)} +O_2(g) \rightarrow CO_2(g)\,;$
$\Delta _rH^o=-395.5 \, kJ\,mol^{-1}$
$H_2 (g) + \frac{1}{2} O_2 (g) \rightarrow H_2O(l)\,;$ $\Delta _rH^o =-285.8\, kJ\, mol^{-1}$
$CO_2(g) + 2H_2O(l) \rightarrow CH_4(g) + 2O_2(g)\,;$
$\Delta _rH^o = + 890.3\, kJ\, mol^{-1}$
Based on the above thermochemical equations, the value of, $\Delta _rH^o $ at $298\, K$ for the reaction
$C_{(graphite)} + 2H_2(g) \rightarrow CH_4(g) $ will be for $\Delta_{r} H^{\circ}$ ........... $kJ \,mol^{-1}$

