Question

Calculate the number of \( \text{Ca}^{2+} \) ion in 222 g anhydrous calcium chloride? (At. Mass Ca = 40, Cl = 35.5)

• A. \( N_A \)
• B. \( 2N_A \)
• C. \( 3N_A \)
• D. \( 4N_A \)

Hint:

For ionic compounds, the number of ions in a given mass is calculated using Avogadro's number, which gives the number of formula units (ions) per mole.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We need to find the total number of calcium ions in a given mass of anhydrous calcium chloride (\( \text{CaCl}_2 \)).
Step 2: Key Formula or Approach:
1. Calculate the molar mass of \( \text{CaCl}_2 \).
2. Find the number of moles of \( \text{CaCl}_2 \).
3. Determine the moles of \( \text{Ca}^{2+} \) ions and multiply by Avogadro's number (\( \text{N}_{\text{A}} \)).
Step 3: Detailed Explanation:
Molar mass of \( \text{CaCl}_2 = 40 + 2(35.5) = 40 + 71 = 111 \text{ g/mol} \).
Number of moles of \( \text{CaCl}_2 \):
\[ n = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{222}{111} = 2 \text{ mol} \] From the chemical formula \( \text{CaCl}_2 \), 1 mole of calcium chloride contains 1 mole of \( \text{Ca}^{2+} \) ions.
Therefore, 2 moles of \( \text{CaCl}_2 \) contain 2 moles of \( \text{Ca}^{2+} \) ions.
Number of \( \text{Ca}^{2+} \) ions = \( 2 \times \text{N}_{\text{A}} \).
Step 4: Final Answer:
The number of ions is \( 2\text{N}_{\text{A}} \).