Question

How many moles are in 7.2x10^15 atoms of Pb?​

Answer 1

1.2 × 10⁻⁸ mol Pb

General Formulas and Concepts:

Math

Pre-Algebra

Order of Operations: BPEMDAS

1. Brackets
2. Parenthesis
3. Exponents
4. Multiplication
5. Division
6. Addition
7. Subtraction

• Left to Right

Chemistry

Atomic Structure

• Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Stoichiometry

• Using Dimensional Analysis

Step-by-step explanation:

Step 1: Define

[Given] 7.2 × 10¹⁵ atoms Pb

Step 2: Identify Conversions

Avogadro's Number

Step 3: Convert

1. [DA] Set up:
   `\displaystyle 7.2 \cdot 10^(15) \ atoms \ Pb((1 \ mol \ Pb)/(6.022 \cdot 10^(23) \ atoms \ Pb))`
2. [DA] Multiply/Divide [Cancel out units]:
   `\displaystyle 1.19562 \cdot 10^(-8) \ mol \ Pb`

Step 4: Check

Follow sig fig rules and round. We are given 2 sig figs.

1.19562 × 10⁻⁸ mol Pb ≈ 1.2 × 10⁻⁸ mol Pb