Question

solid calcium chloride is needed to make 500 ml of a 1.0 molar standard solution?

Answer 1

To prepare a 1.0 M solution of calcium chloride (CaCl₂), you need to calculate the amount of solid calcium chloride required.

1. **Define the volume and molarity**:
- Volume of solution (V) = 500 mL = 0.500 L
- Molarity (M) = 1.0 M

2. **Use the formula for molarity**:
\[
M = \frac{n}{V}
\]
Rearranging this formula to find the number of moles (n):
\[
n = M \times V
\]
Substituting the values:
\[
n = 1.0 \, \text{mol/L} \times 0.500 \, \text{L} = 0.500 \, \text{mol}
\]

3. **Calculate the mass of CaCl₂ needed**:
- First, calculate the molar mass of calcium chloride (CaCl₂):
- Ca (Calcium) = 40.08 g/mol
- Cl (Chlorine) = 35.45 g/mol (and there are 2 chlorine atoms)
- Molar mass of CaCl₂ = 40.08 g/mol + (2 × 35.45 g/mol) = 40.08 g/mol + 70.90 g/mol = 110.98 g/mol

- Now, use the number of moles to find the mass:
\[
\text{Mass} = n \times \text{molar mass}
\]
\[
\text{Mass} = 0.500 \, \text{mol} \times 110.98 \, \text{g/mol} = 55.49 \, \text{g}
\]

Therefore, you will need **55.49 grams** of solid calcium chloride to make 500 mL of a 1.0 M standard solution.