Question

CH4 + 202 → CO2 + 2H2O
How many moles of O2 needed to react with 32 grams of CH4?

Answer 1

Answer:

4.0 mol O₂

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

Stoichiometry

• Using Dimensional Analysis

Explanation:

Step 1: Define

[RxN - Balanced]   CH₄ + 2O₂ → CO₂ + 2H₂O

[Given]   32 g CH₄

Step 2: Identify Conversions

[RxN] 1 mol CH₄ → 2 mol O₂

Molar Mass of C - 12.01 g/mol

Molar Mass of H - 1.01 g/mol

Molar Mass of CH₄ - 12.01 + 4(1.01) = 16.05 g/mol

Step 3: Stoichiometry

1. Set up conversion:                    $\displaystyle 32 \ g \ CH_4(\frac{1 \ mol \ CH_4}{16.05 \ g \ CH_4})(\frac{2 \ mol \ O_2}{1 \ mol \ CH_4})$
2. Divide/Multiply:                          $\displaystyle 3.98754 \ mol \ O_2$

Step 4: Check

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

3.98754 mol O₂ ≈ 4.0 mol O₂