Answer:
3.16 × 10²¹ atoms MgCl₂
General Formulas and Concepts:
- Avagadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
- Molar Mass - how many grams of an element/compound in 1 mol of that substance
- Reading a Periodic Table of Elements
Explanation:
Step 1: Define
0.500 g MgCl₂ (Magnesium Chloride)
- Mg has a 2+ charge
- Cl has a 1- charge
- Need to balance the charges
Step 2: Define conversion
Molar Mass of Mg - 24.31 g/mol
Molar Mass of Cl - 35.45 g/mol
Molar Mass of MgCl₂ - 24.31 + 2(35.45) = 95.21 g/mol
Avagadro's Number: atoms
Step 3: Dimensional Analysis
[tex]0.500 \ g \ MgCl_2(\frac{1 \ mol \ MgCl_2}{95.21 \ g \ MgCl_2} )(\frac{6.022 \cdot 10^{23} \ atoms \ MgCl_2}{1 \ mol \ MgCl_2} )[/tex] = 3.16248 × 10²¹ atoms MgCl₂
Step 4: Check
We are given 3 sig figs. Follow sig fig rules.
3.16248 × 10²¹ atoms MgCl₂ ≈ 3.16 × 10²¹ atoms MgCl₂
