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.

9.9 × 10²⁰ molecules O₂

General Formulas and Concepts:

Math

Pre-Algebra

Order of Operations: BPEMDAS

Brackets Parenthesis Exponents Multiplication Division Addition 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 AnalysisExplanation:

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

Set up:                              Multiply/Divide:                                                                                              

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

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