CourseLesson 1 of 5

Stoichiometry, Moles & Chemical Equations

Part 1 of 3

1. Mole Calculations and Avogadro's Constant

The mole bridges macroscopic mass to microscopic particles via Avogadro's number, providing the foundation for chemical stoichiometry.

Avogadro's Number

N_A = 6.022 × 10²³ entities/mol

Links formula units, atoms, or molecules to molar quantities

Mass to Moles

n = m / M

m is mass in grams; M is molar mass in g/mol

Solution Moles

n = M × V

M is molarity in mol/L; V is solution volume in liters

Molar Gas Volume

V_m = 22.4 L/mol at STP

Standard temperature (0°C, 273.15 K) and pressure (1 atm)

Worked example

1Calculate moles and molecule count in 36.0 g of pure water (H2O, M = 18.0 g/mol).
2Moles n = 36.0 g / 18.0 g/mol = 2.0 mol H2O.
3Molecule count N = 2.0 mol × (6.022 x 10²³ molecules/mol) = 1.204 x 10²⁴ H2O molecules.

1.The formula relating mass (g) and molar mass (g/mol) to chemical amount is n = m / M.

2.One mole of any gas at STP occupies a volume of exactly 1.0 Litre.

3.Avogadro's constant specifies 6.022 x 10²³ entities per mole of substance.

Study assistant

Paid students only — a preview

Why is this the correct answer?

Eliminate any option that contradicts something stated directly in the lesson, then check which one actually follows from the rule you just learned. Tell me which option confused you and I'll point to the exact line.

Exam strategy

If you can explain why the wrong answers are wrong, you know the topic. Remembering the right one only gets you halfway.

Unlock AI tutoring for this exam →

This is a free preview lesson

Unlock all 29 lessons across 6 subjects, the drills, and full timed mock exams for CEnT-S.

Atomic Structure, Periodic Trends & Chemical Bonding