Question

Calculate the number of molecules in

3.7 x 10-2 Liters of oxygen gas at STP. Round your answer to the nearest whole number.

Answer 1

9.9 × 10²⁰ molecules 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

• Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
• STP (Standard Conditions for Temperature and Pressure) = 22.4 L per mole at 1 atm, 273 K

Stoichiometry

• Using Dimensional Analysis

Step-by-step explanation:

Step 1: Define

3.7 × 10⁻² L O₂ at STP

Step 2: Identify Conversions

[STP] 22.4 L/mol

Avogadro's Number

Step 3: Convert

1. Set up:
   `\displaystyle 3.7 \cdot 10^(-2) \ L \ O_2((1 \ mol \ O_2)/(22.4 \ L \ O_2 \ at \ STP))((6.022 \cdot 10^(23) \ molecules \ O_2)/(1 \ mol \ O_2))`
2. Multiply/Divide:
   `\displaystyle 9.94705 \cdot 10^(20) \ molecules \ O_2`

Step 4: Check

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

9.94705 × 10²⁰ molecules O₂ ≈ 9.9 × 10²⁰ molecules O₂