Answer:
0.279 g He
General Formulas and Concepts:
Math
Pre-Algebra
Order of Operations: BPEMDAS
- Brackets
- Parenthesis
- Exponents
- Multiplication
- Division
- Addition
- Subtraction
Chemistry
Atomic Structure
- Reading a Periodic Table
- Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
Stoichiometry
- Using Dimensional Analysis
Explanation:
Step 1: Define
4.20 × 10²² molecules He
Step 2: Identify Conversions
Avogadro's Number
[PT] Molar Mass of He - 4.00 g/mol
Step 3: Convert
- Set up: [tex]\displaystyle 4.20 \cdot 10^{22} \ molecules \ He(\frac{1 \ mol \ He}{6.022 \cdot 10^{23} \ molecules \ He})(\frac{4.00 \ g \ He}{1 \ mol \ He})[/tex]
- Multiply/Divide: [tex]\displaystyle 0.278997 \ g \ He[/tex]
Step 4: Check
Follow sig fig rules and round. We are given 3 sig figs.
0.278997 g He ≈ 0.279 g He
