Question

Amount of sodium hydroxide present in $500ml$ of $0.2M$ solutions is :

• A. $4gm$
• B. $8gm$
• C. $40gm$
• D. $20gm$

Answer 1

The correct option is A $4gm$

Molarity (M) : The number of moles of a solute dissolved in 1 L (1000 ml) of the solution is known as the molarity of the solution.

Molarity of a solution

$\left(M\right)=\frac{\text{mass of solute}}{\text{molar mass of solute}}\times \frac{1000}{\text{volume of solution in mL}}$

$\therefore 0.2=\frac{w}{40}\times \frac{1000}{500}$

so $w=4gm$.

Amount of sodium hydroxide present in 500ml of 0.2M solutions is 4 gm.