The heats of combustion Delta H of CH_4,C_2H_ | vedclass

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(A) The best fuel is determined by the highest calorific value,which is the amount of heat released per unit mass of the fuel.Calorific value $= \frac

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$CH_4$

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(A) The best fuel is determined by the highest calorific value,which is the amount of heat released per unit mass of the fuel.Calorific value $= \frac{\Delta H}{	ext{Molar Mass}}$.For $CH_4$ $(M = 16 \ g/mol)$: $\frac{-212.8}{16} = -13.30 \ kcal/g$.For $C_2H_6$ $(M = 30 \ g/mol)$: $\frac{-373.0}{30} = -12.43 \ kcal/g$.For $C_2H_4$ $(M = 28 \ g/mol)$: $\frac{-337.0}{28} = -12.04 \ kcal/g$.For $C_2H_2$ $(M = 26 \ g/mol)$: $\frac{-310.5}{26} = -11.94 \ kcal/g$.Since $CH_4$ has the highest magnitude of heat released per gram,it is the best fuel.

$(a)$ Entropy of vaporization	$(1)$ Decreases
$(b)$ $K$ for spontaneous process	$(2)$ Always has a $(+)$ value
$(c)$ Crystalline solid state	$(3)$ Has minimum entropy
$(d)$ $\Delta U$ for adiabatic expansion of an ideal gas	$(4)$ $\frac{\Delta H_{vap}}{T_b}$

The heats of combustion $\Delta H$ of $CH_4$,$C_2H_6$,$C_2H_4$,and $C_2H_2$ gases are $-212.8$,$-373.0$,$-337.0$,and $-310.5 \ kcal$ respectively at the same temperature. Which of these gases is the best fuel?

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