$C + O _{2}( g ) \rightarrow CO _{2} \cdots \cdots( i )$ $\Delta H =-\,393 \,kJ\,mol ^{-1}$

$H _{2}+\frac{1}{2} O _{2} \rightarrow H _{2} O , \cdots \cdots( ii )$ $\Delta H =-\,287.3 \,kJ\,mol ^{-1}$

$2 CO _{2}+3 H _{2} O \rightarrow C _{2} H _{5} OH +3 O _{2} \cdots \cdots ( iii )$; $ \Delta H =1366.8 \,kJ\,mol ^{-1}$

$C _{2} H _{5} OH (1)$ માટે ની રચનાની પ્રમાણિત એન્થાલ્પી શોધો

Question

$C + O _{2}( g ) \rightarrow CO _{2} \cdots \cdots( i )$ $\Delta H =-\,393 \,kJ\,mol ^{-1}$

$H _{2}+\frac{1}{2} O _{2} \rightarrow H _{2} O , \cdots \cdots( ii )$ $\Delta H =-\,287.3 \,kJ\,mol ^{-1}$

$2 CO _{2}+3 H _{2} O \rightarrow C _{2} H _{5} OH +3 O _{2} \cdots \cdots ( iii )$; $ \Delta H =1366.8 \,kJ\,mol ^{-1}$

$C _{2} H _{5} OH (1)$ માટે ની રચનાની પ્રમાણિત એન્થાલ્પી શોધો

AIIMS 2019, Medium

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Solution

d
$C + O _{2}( g ) \rightarrow CO _{2} \cdots \cdots( I )$

The enthalpy change for the above reaction is $-\,393\, kJ \,mol ^{-1}$

$H _{2}+\frac{1}{2} O _{2} \rightarrow H _{2} O \cdots \cdots( II )$

The enthalpy change for the above reaction is $-287.3\, kJ \,mol ^{-1}$

$2 CO _{2}+3 H _{2} O \rightarrow C _{2} H _{5} OH +3 O _{2} \cdots \cdots( III )$

The enthalpy change for the above reaction is $1366.8\,kJ \,mol ^{-1}$

The formation reaction of $C _{2} H _{5} OH (l)$ is as follows :

$2 C +3 H _{2}+\frac{1}{2} O _{2} \rightarrow C _{2} H _{5} OH$

To derive the above reaction, multiply reaction $(I)$ by $2$, multiply reaction $(II)$ by $3$ and then add all the reactions.

Therefore, the total change in enthalpy will become as :

$\Delta H=-\,393\, kJ \,mol ^{-1} \times 2+\left(-287.3 \,kJ \,mol ^{-1}\right) \times 3+$$1366.8 \,kJ \,mol ^{-1}$

$\Delta H=-\,281.1 \,kJ \,mol ^{-1}$

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