The heat of combustion of ethanol into carbon dioxides and water … - Vidyadip

MCQ

The heat of combustion of ethanol into carbon dioxides and water is $-327\, kcal$ at constantpressure. The heat evolved (in cal) at constant volume and $27^{\circ} C$ (if all gases behave ideally) is $\left( R =2\, cal\, mol ^{-1}\, K ^{-1}\right)$

✓
$326400$
B
$312400$
C
$322425$
D
$322500$

✓

Answer

Correct option: A.

$326400$

a
$C _{2} H _{5} OH _{(\ell)}+3 O _{2( g )} \longrightarrow 2 CO _{2( g )}+3 H _{2} O _{(\ell)}$

$\Delta n _{ g }=2-3=-1$

$\Delta_{ C } H =\Delta_{ c } U +\left(\Delta n _{ g }\right) RT$

$\Delta_{ c } H =\Delta_{ c } U - RT$

$\Delta_{ c } U =\Delta_{ c } H + RT$

$=-327 \times 10^{3}+2 \times 300$

$=-326400 cal$

: Heat evolved

$=326400 cal$

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