Answer
a. 63 mL of the original 20. % (m/v) glucose solution.
b. 9.0 mL of the original 5.0 % (m/v) $CaCl_2$ solution.
c. 33.3 mL of the original 18.0 M $H_2SO_4$ solution.
Work Step by Step
1. Write the dilution expression, and solve for the initial volume $(V_1)$
$C_1V_1 = C_2V_2$
$$V_1 = \frac{C_2V_2}{C_1} $$
a.
2. Substitute the values and calculate the initial volume:
$$V_1 = \frac{(250 \space mL)(5.0 \space \% (m/v))}{20. \space \% (m/v)}$$
$$V_1 = 63 \space mL$$
b.
2. Substitute the values and calculate the initial volume:
$$V_1 = \frac{(45.0 \space mL)(1.0 \space \% (m/v))}{5.0 \space \% (m/v)}$$
$$V_1 = 9.0 \space mL$$
c.
2. Substitute the values and calculate the initial volume:
$$V_1 = \frac{(100. \space mL)(6.00 \space M)}{18.0 \space M}$$
$$V_1 = 33.3 \space mL$$
