Question

How many atoms are present in a sample of Calcium (Ca) weighing 127.38g?

Answer 1

Answer:

1.9139 × 10²⁴ atoms Ca

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

127.38 g Ca

Step 2: Identify Conversions

Avogadro's Number

Molar Mass of Ca - 40.08 g/mol

Step 3: Convert

$127.38 \ g \ Ca(\frac{1 \ mol \ Ca}{40.08 \ g \ Ca} )(\frac{6.022 \cdot 10^{23} atoms \ Ca}{1 \ mol \ Ca} )$ = 1.91388 × 10²⁴ atoms Ca

Step 4: Check

We are given 5 sig figs. Follow sig fig rules and round.

1.91388 × 10²⁴ atoms Ca ≈ 1.9139 × 10²⁴ atoms Ca