Question

How many atoms are present in 8.00g of He?

Answer 1

Answer:

1.20 × 10²⁴ atoms He

General Formulas and Concepts:

Chemistry - Atomic Structure

• Reading a Periodic Table
• Using Dimensional Analysis
• Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Explanation:

Step 1: Define

8.00 g He

Step 2: Identify Conversions

Avogadro's Number

Molar Mass of He - 4.00 g/mol

Step 3: Convert

$8.00 \ g \ He(\frac{1 \ mol \ He}{4.00 \ g \ He} )(\frac{6.022 \cdot 10^{23} \ atoms \ He}{1 \ mol \ He} )$ = 1.2044 × 10²⁴ atoms He

Step 4: Check

We are given 3 sig figs. Follow sig fig rules and round.

1.2044 × 10²⁴ atoms He ≈ 1.20 × 10²⁴ atoms He