Question

25 mL of 3 M HCl were added to 75 mL of 0.05 M HCl. The molarity of HCl in the resulting solution is approximately

• A. 0.055 M
• B. 0.35 M
• C. 0.787 M
• D. 3 .05 M

Answer 1

Answer: (C)

0.787 M

Answer 2

Molarity of resulting solution $M_{Total} = \frac{M_1V_1}{V_{Total}} + \frac{M_2V_2}{V_{Total}}$ = $\frac{25 \times 3}{100} + \frac{75 \times 0.05}{100}$ = 0.75 + 0.0375 = 0.7875 M.