Answer
a. $0.900$ M $HCl$ solution.
b. 6.00 % (m/v) $NH_4Cl$ solution.
c. 0.510 M $KOH$ solution.
Work Step by Step
1. Write the dilution expression, and solve for the final concentration $(C_2)$
$C_1V_1 = C_2V_2$
$$\frac{C_1V_1}{V_2} = C_2$$
a.
2. Substitute the values and calculate the final concentration:
$$C_2 = \frac{(25.0 \space mL)(18.0 \space M)}{500. \space mL}$$
$$C_2 = 0.900 \space M$$
b.
2. Substitute the values and calculate the final concentration:
$$C_2 = \frac{(50.0 \space mL)(15.0 \space \% (m/v))}{125 \space mL}$$
$$C_2 = 6.00 \space \% (m/v)$$
c.
2. Substitute the values and calculate the final concentration:
$$C_2 = \frac{(4.50 \space mL)(8.50 \space M)}{75.0 \space mL}$$
$$C_2 = 0.510 \space M$$