Question

Which of the following statement is correct?

• A. More the number of carbon atoms, lesser is the heat of combustion.
• B. More the heat of combustion, lesser is the stability of alkenes.
• C. More the heat of hydrogenation, more is the stability of alkenes.
• D. All of the above.

Answer 1

The correct option is B More the heat of combustion, lesser is the stability of alkenes.

The addition of hydrogen is called as hydrogenation.
The heat released in a hydrogenation reaction is called the heat of hydrogenation $\Delta H_{HOH}^{\circ }$
More the number of $\pi$ bonds more is the heat of hydrogenation.
More the heat of hydrogenation, lesser is the stability of alkenes.
Heat of combustion : The amount of heat liberated when a given amount of the substance undergoes combustion.
For a given hydrocarbon $C_x{H}_y$, the combustion reaction is :
$C_x{H}_y\left(s\right)+(x+\frac{y}{4})O_2\left(g\right)\to xC{O}_2+\left(\frac{y}{2}\right)H_{2}O\left(l\right)$

More the heat of combustion lesser is the stability of alkenes.
More the number of carbon atoms, more is the heat of combustion.