Question

Consider seperate solutions of $0.500M{C}_2{H}_{5}OH\left(aq\right),0.250MKBr\left(aq\right)$, $0.125MN{a}_{3}P{O}_4\left(aq\right)$ and $0.1MM{g}_3(P{O}_4{)}_2$ at ${25}^{\circ }C$.

Which statement is true about these solutions, assuming all salts to be strong electrolytes?

• A. $0.125$ $M$ $N{a}_{3}P{O}_4\left(aq\right)$ has the highest osmotic pressure.
• B. $0.500$ $M$ $C_2{H}_{5}OH\left(aq\right)$ has the highest osmotic pressure.
• C. They all have the same osmotic pressure.
• D. $0.100$ $M$ $M{g}_3\left(P{O}_4{)}_2\right(aq)$ has the highest osmotic pressure

Answer 1

The correct option is C They all have the same osmotic pressure.

For $C_2{H}_{5}OH,\pi =1\times 0.5\times RT$

For $KBr,\pi =2\times 0.25\times RT$

For $M{g}_3(P{O}_4{)}_2,\pi =5\times 0.1\times RT$

For $N{a}_{3}P{O}_4,\pi =4\times 0.125\times RT$

So, all are isotonic solutions.