Question

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

Answer 1

Mass of O₂ needed = 64 g

Further explanation

Given

Reaction

CH₄ + 2O₂ → CO₂ + 2H₂O

36 grams of H₂O

Required

Mass of O₂ needed

Solution

mol H₂O :

= mass : MW H₂O

= 36 : 18 g/mol

= 2

From the equation, mol ratio of O₂ : H₂O = 2 : 2, so mol O₂=2

Mass O₂ :

= mol x MW O₂

= 2 x 32 g/mol

= 64 g

Answer 2

64 g 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

Step-by-step explanation:

Step 1: Define

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

[Given] 36 g H₂O

[Solve] x g O₂

Step 2: Identify Conversions

[RxN] 2 mol O₂ → 2 mol H₂O

[PT] Molar Mass of O - 16.00 g/mol

[PT] Molar Mas of H - 1.01 g/mol

Molar Mass of O₂ - 2(16.00) = 32.00 g/mol

Molar Mass of H₂O - 2(1.01) + 16.00 = 18.02 g/mol

Step 3: Stoichiometry

1. Set up conversion:
   `\displaystyle 36 \ g \ H_2O((1 \ mol \ H_2O)/(18.02 \ g \ H_2O))((2 \ mol \ O_2)/(2 \ mol \ H_2O))((32.00 \ g \ O_2)/(1 \ mol \ O_2))`
2. Divide/Multiply [Cancel Units]:
   `\displaystyle 63.929 \ g \ O_2`

Step 4: Check

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

63.929 g O₂ ≈ 64 g O₂