Given that C+O_2 arrow CO_2 ; Δ H^ =-a ~kJ . 2 CO+O_2 arrow 2 CO_2 ; Δ H^ =-b ~kJ The heat of formation of CO is

Correct answer: C. (b-2 a)/(2) aligned & : C+O_2 arrow CO_2 ; Δ H^ =-a ~kJ & 2 CO+O_2 arrow 2 CO_2 ; Δ H^ =-b ~kJ aligned Formation of CO can be written as : C+(1)/(2) O_2 arrow CO ; Δ H^ =? Adding equation: C+O_2 arrow CO_2 ; Δ H^ =-a ~kJ CO_2 arrow CO+(1)/(2) O_2 ; Δ H^ =(b)/(2) ~kJ We get Δ H_f^ (CO)=(b)/(2)-a=(b-2 a)/(2)

AIIMS 2001

Exam: AIIMS
Year: 2001
Subject: Chemistry
Chapter: Thermodynamics (C)

AIIMS 2001 · Chemistry · Thermodynamics (C)

Given that C+O_2 arrow CO_2 ; Δ H^ =-a ~kJ . 2 CO+O_2 arrow 2 CO_2...

Given that

\mathrm{C}+\mathrm{O}_2 \rightarrow \mathrm{CO}_2 ; \Delta H^{\circ}=-a \mathrm{~kJ}

2 \mathrm{CO}+\mathrm{O}_2 \rightarrow 2 \mathrm{CO}_2 ; \Delta H^{\circ}=-b \mathrm{~kJ}

The heat of formation of

\mathrm{CO}

Options

A $b-2 a$
B $\frac{2 a-b}{2}$
C $\frac{b-2 a}{2}$
D $2 a-b$

Correct answer

C. $\frac{b-2 a}{2}$

Step-by-step solution

\begin{aligned} & : \mathrm{C}+\mathrm{O}_2 \rightarrow \mathrm{CO}_2 ; \Delta H^{\circ}=-a \mathrm{~kJ} \\ & 2 \mathrm{CO}+\mathrm{O}_2 \rightarrow 2 \mathrm{CO}_2 ; \Delta H^{\circ}=-b \mathrm{~kJ} \end{aligned} Formation of

\mathrm{CO}

can be written as :

\mathrm{C}+\frac{1}{2} \mathrm{O}_2 \rightarrow \mathrm{CO} ; \Delta H^{\circ}=?

Adding equation:

\mathrm{C}+\mathrm{O}_2 \rightarrow \mathrm{CO}_2 ; \Delta H^{\circ}=-a \mathrm{~kJ}

\mathrm{CO}_2 \rightarrow \mathrm{CO}+\frac{1}{2} \mathrm{O}_2 ; \Delta H^{\circ}=\frac{b}{2} \mathrm{~kJ}

We get

\Delta H_f^{\circ}(\mathrm{CO})=\frac{b}{2}-a=\frac{b-2 a}{2}

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