Question

Which one of the following electrolytes has the same value of van't Hoff's factor (i) as that of the Hoff's factor (i) as that of the $Al _{2}\left( SO _{4}\right)_{3}$ (if all are $100 \%$ ionised)?

• A. $K_{2}SO_{4}$
• B. $K _{3}\left[ Fe ( CN )_{6}\right]$
• C. $K _{4}\left[ Fe ( CN )_{6}\right]$
• D. $Al \left( NO _{3}\right)_{3}$

Answer 1

Answer: (C)

van't Hoff factor of $Al _{2}\left( SO _{4}\right)_{3} \rightarrow 2 Al ^{+3}+3 SO _{4}^{-2}$

So $n=5$ $K _{4}\left[ Fe ( CN )_{6}\right] \rightarrow 4 K ^{+}+\left[ Fe ( CN )_{6}\right]^{-4}$

So $n =5$

As $\alpha=100 \%=1$

$i=n=5$

$\ln K _{2} SO _{4} i =2$, In $K _{3}\left[ Fe ( CN )_{6}\right] i =4,$ In $Al \left( NO _{3}\right)_{3} i =4$