Question

Determine the mass in grams of 2.71 x 10^21 atoms of arsenic if the mass of one mole is 74.92g

Answer 1

0.337 g As

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

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

Stoichiometry

• Using Dimensional Analysis

Step-by-step explanation:

Step 1: Define

[Given] 2.71 × 10²¹ atoms As

[Solve] grams As

Step 2: Identify Conversions

Avogadro's Number

[PT] Molar Mass of As - 74.92 g/mol

Step 3: Convert

1. [DA] Set up:
   `\displaystyle 2.71 \cdot 10^(21) \ atoms \ As((1 \ mol \ As)/(6.022 \cdot 10^(23) \ atoms \ As))((74.92 \ g \ As)/(1 \ mol \ As))`
2. [DA] Multiply/Divide [Cancel out units]:
   `\displaystyle 0.337152 \ g \ As`

Step 4: Check

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

0.337152 g As ≈ 0.337 g As