Question

0.25 moles of sodium chloride are dissolved in water to make a 500 mL solution. The molarity of the $C{l}^{-}$ ions is :

• A. 0.50 M
• B. 0.25 M
• C. 1.50 M
• D. 2.00 M

Answer 1

The correct option is A 0.50 M

We know,
$\text{Molarity}=\frac{\text{moles of NaCl}}{\text{total volume of solution (mL)}}\times 1000=\frac{0.25}{500}\times 1000=0.5M$

Again,
$NaCl\to N{a}^{+}+C{l}^{-}$
1 mole of $NaCl$ dissociates to give 1 mole of $C{l}^{-}$ ions,
Thus, 0.25 moles $NaCl$ gives 0.25 moles of $C{l}^{-}$ ions

Since number of moles of $C{l}^{-}$ is same as $NaCl$, thus molarity of $C{l}^{-}$ is also 0.5 M.