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  • The standard heat of combustion of solid boron is equal to :Option: 1 <img alt="\Delta H^{0}_{f}\left ( B_{2}O_{3} \right )" src="https://learn.caree

The standard heat of combustion of solid boron is equal to :

Option: 1

\Delta H^{0}_{f}\left ( B_{2}O_{3} \right )


Option: 2

1/2\Delta H^{0}f\left ( B_{2}O_{3} \right )


Option: 3

2\Delta H^{0}f\left ( B_{2}O_{3} \right )


Option: 4

1/3\Delta H^{0}f\left ( B_{2}O_{3} \right )


Answers (1)

best_answer

Enthalpy of combustion -

Amount of Enthalpy change when 1 mole of substance is completly burn in excess of Oxygen

CO+\frac{1}{2}O_{2}\rightarrow CO_{2};\;\;\;\Delta H=-68.3\;kcal

 

Combustion reaction of solid boron

B\left ( s \right )+\frac{3}{4}O_{2}\left ( g \right )\rightarrow \frac{1}{2}B_{2}O_{3}\left ( s \right )

\Delta H^{\circ}_{c}=\frac{1}{2}\Delta H^{\circ}_{f}\left ( B_{2} O_{3},s\right )-\Delta H^{\circ}_{f}\left ( B,s \right )-\frac{3}{4}\Delta H^{\circ}_{f}\left ( O_{2},g \right )

\Delta H^{\circ}_{f}  of element in stable state of aggregation is assumed to be zero.

\Delta H^{\circ}C=\frac{1}{2}\; \Delta H^{\circ}f\left ( B_{2}O_{3},s \right )

Therefore, Option(2) is correct.

Posted by

shivangi.bhatnagar

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