A aqueous solution of at exerts an osmotic pressure of exactly . What is the apparent percentage ion — Solutions and Colligative Properties Chemistry Question
Question
A $0.1\text{ M}$ aqueous solution of $MgCl_2$ at $300\text{ K}$ exerts an osmotic pressure of exactly $4.92\text{ atm}$. What is the apparent percentage ionization of the salt in this specific solution? ($R = 0.082\text{ L atm K}^{-1}\text{ mol}^{-1}$).
Answer: B
💡 Solution & Explanation
The theoretical osmotic pressure $\pi_{ideal} = CRT = 0.1 \times 0.082 \times 300 = 2.46\text{ atm}$. Experimental $\pi = 4.92\text{ atm}$. Thus $i = 4.92 / 2.46 = 2.0$. For $MgCl_2$, $n=3$. Using $i = 1 + \alpha(n-1) \implies 2 = 1 + 2\alpha \implies 2\alpha = 1 \implies \alpha = 0.50$, which is $50\%$.
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