Question

Degree of dissociation of pure $H_{2}O$ is $1.9\times 10^{-9}$ Molar ionic conductances of $H^{+}\&O{H}^{-}$ ions at infinite dilution are $200Sc{m}^{2}mo{l}^{-1}\&350Sc{m}^2$ $mo{l}^{-1}$ respectively. Molar conductance of water is:

• A. $3.8\times 10^{-7}Sc{m}^{2}mo{l}^{-1}$
• B. $5.7\times 10^{-7}Sc{m}^{2}mo{l}^{-1}$
• C. $9.5\times 10^{-7}Sc{m}^{2}mo{l}^{-1}$
• D. $1.045\times 10^{-6}Sc{m}^{2}mo{l}^{-1}$

Answer 1

Answer: (D)

$\alpha =\frac{{\Lambda }_m^c}{{\Lambda }_m^{\infty }}$

${\Lambda }_m^{\infty }\left(H_{2}O\right)={\lambda }_m^{\infty }\left(H^{+}\right)+{\lambda }_m^{\infty }\left(O{H}^{-}\right)$

$\Rightarrow 1.9\times 10^{-9}=\frac{{\Lambda }_m^c}{550Sc{m}^{2}mo{l}^{-1}}$ $=200+350\Rightarrow 550$

${\Lambda }_m^c=550\times 1.9\times 10^{-9}Sc{m}^{2}mo{l}^{-1}$

$=1.045\times 10^{-6}Sc{m}^{2}mo{l}^{-1}$