Question

How much water should be added to 100 mL of 1 M HCl to make it 0.25 M?

• A. 100 mL
• B. 200 mL
• C. 300 mL
• D. 400 mL

Hint:

Use the dilution equation \( C_1 V_1 = C_2 V_2 \) to find the final volume and subtract initial volume to find how much solvent to add.

Answer 1

The Correct Option is C

Step 1: Use the dilution formula: \[ C_1 V_1 = C_2 V_2 \] where,
\( C_1 = 1 \, M \) (initial concentration),
\( V_1 = 100 \, \text{mL} \) (initial volume),
\( C_2 = 0.25 \, M \) (final concentration),
\( V_2 = ? \) (final volume). Step 2: Calculate \( V_2 \): \[ V_2 = \frac{C_1 V_1}{C_2} = \frac{1 \times 100}{0.25} = 400 \, \text{mL} \] Step 3: Volume of water to be added = Final volume - Initial volume \[ = 400 - 100 = 300 \, \text{mL} \] Step 4: Therefore, 300 mL of water should be added.