Thermodynamics and Thermochemistry 2 Question 33
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33. Enthalpy of dissociation (in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) of acetic acid obtained from the Expt. 2 is
======= ####33. Enthalpy of dissociation (in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) of acetic acid obtained from the Expt. 2 is
3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed (a) 1.0
(b) 10.0
(c) 24.5
(d) 51.4
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Solution:
- Let $C \mathrm{JK}^{-1}$ be the heat capacity of calorimeter.
Mass of solution $=200 \mathrm{~mL} \times 1 \mathrm{~g} \mathrm{~mL}^{-1}=200 \mathrm{~g}$
Heat evolved in Expt. 1
$$ \begin{aligned} & =57 \times 1000 \times 0.1(\mathrm{~mol})=5700 \mathrm{~J} \ \Rightarrow 5700 \mathrm{~J} & =(200 \times 4.2+C) \times 5.7 \ \Rightarrow \quad 1000 & =200 \times 4.2+C \end{aligned} $$
Let $x \mathrm{~kJ} / \mathrm{mol}$ is heat evolved in neutralisation of acetic acid.
$\Rightarrow x \times 1000 \times 0.10=(200 \times 4.2+C) \times 5.6$
$\Rightarrow \quad \frac{x \times 100}{5.6}=200 \times 4.2+C$
From (i) and (ii) : $x=56 \mathrm{~kJ} / \mathrm{mol}$
$\Rightarrow$ Enthalpy of ionisation of acetic acid
$$ =-56-(-57)=1 \mathrm{~kJ} / \mathrm{mol} $$
