Question

Suppose you were making 100.0 mL of a solution that is 0.040 M KCl. What mass of KCl should you weigh to make this solution?

Answer 1

Answer:

mass = 0.2982 grams

Explanation:

Given that;

volume = 100.0 mL = 0.1 L

Molarity =0.040 M

Since Molarity = $\frac{no of moles }{volume}$

$0.040 M = \frac{x}{0.1}$

(x) no of moles = 0.040 × 0.1

= 0.004 moles

Also; to calculate the  mass of KCl should you weigh to make this solution;

we have;

no of moles =$\frac{mass}{molar mass}$

molar mass of KCl = 74.55 g/mol

∴

0.004 moles = $\frac{mass}{74.55g/mol}$

mass = 0.004 moles * 74.55 $\frac{g}{mol}$

mass = 0.2982 grams

Hence, the mass of KCl should you weigh to make this solution is  0.2982 grams