The amount of water that must be added to a 3 M HCl solution to make a 60 mL solution of 2 M HCl is ______ mL.

Answer 1

Molarity of original solution (M1) = 3 M

Volume of original solution ($V_1$) = ?

Molarity of final solution ($M_2$) = 2 M

Volume of final solution ($V_2$) = 0.060 L = 60 mL

By law of dilution, $V_1 M_1 = V_2M_2$

$V_1=\large\frac{2\times 60}{3}$$=40mL$

Volume of water added = 60 mL − 40 mL = 20 mL

Hence (A) is the correct answer.