Question

How many grams of CaCl2 should be dissolved in 504.3 mL of water to make a 0.40 M solution of CaCl2?

Answer 1

22.39 grams.

Step-by-step explanation

How many moles of CaCl₂ in that solution?

`c = 0.40 \; \text{M} = 0.40 \; \text{mol}\cdot \textbf{L}^(-1)`;

`V = 504.3 \; \textbf{ml} = 0.5043 \; \textbf{L}`;

`n = c \cdot V = 0.40 \; \text{mol}\cdot \textbf{L}^(-1) * 0.5043 \; \textbf{L}= 0.20172 \; \text{mol}`.

What's the mass of that 0.20172 moles of CaCl₂?

Molar mass from a modern periodic table:

• Ca- 40.078;
• Cl- 35.45.

Molar mass of CaCl₂:

`M(\text{CaCl}_2) = 40.078 + 2 * 35.45 = 110.978 \; \text{g}\cdot \text{mol}^(-1)`.

Mass of that 0.20172 moles of CaCl₂:

`m = n \cdot M = 0.20172 * 110.978 = 22.39 \; \text{g}`.