To 25mL of 0.90M HCl, 275mL do distilled water is added. What is the molarity of the resulting solution?

0.075 M.

Explanation:

It is a dilution process. We have the rule states that the no. of millimoles before dilution is equal to the no. of millimoles after dilution.

(MV) before dilution = (MV) after dilution

M before dilution = 0.90 M.

V before dilution = 25.0 mL.

M after dilution = ? M.

V after dilution = V of HCl + V of water added = 25.0 mL + 275.0 mL = 300.0 mL.

∴ M after dilution = (MV) before dilution / V after dilution = (0.90 M) (25.0 mL) / (300.0 mL) = 0.075 M.