Question

CH4 + 202 → CO2 + 2H2O
How many moles of O2, needed to produce 36 grams of H20?

Answer 1

Answer:

2.0 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]   36 g H₂O

Step 2: Identify Conversions

[RxN] 2 mol H₂O → 2 mol O₂

Molar Mass of H - 1.01 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of H₂O - 18.02 g/mol

Step 3: Stoichiometry

1. Set up:                              $\displaystyle 36 \ g \ H_2O(\frac{1 \ mol \ H_2O}{18.02 \ g \ H_2O})(\frac{2 \ mol \ O_2}{2 \ mol \ H_2O})$
2. Divide/Multiply:                $\displaystyle 1.99778 \ mol \ O_2$

Step 4: Check

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

1.99778 mol O₂ ≈ 2.0 mol O₂