Stoichiometry
10th Grade Science · 8 lessons
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Lessons in this unit
- 1Relative Formula MassThe relative formula mass of a compound is the sum of the relative atomic masses of every atom in its formula. Water is 2 × 1 + 16 = 18; calcium carbonate, CaCO₃, is 40 + 12 + 48 = 100. Everything quantitative in chemistry starts here.Lesson
- 2The Mole and Avogadro's ConstantA mole is the amount of substance containing 6.02 × 10²³ particles — Avogadro's constant. One mole of any substance has a mass in grams equal to its relative formula mass, which is what makes counting atoms by weighing possible.Experiment
- 3Moles, Mass and Formula MassMoles equals mass divided by relative formula mass, n = m/Mr. Rearranged, it converts between what you can weigh and what actually reacts. Most quantitative chemistry problems are this triangle applied twice with a balanced equation in between.Lesson
- 4Balancing Chemical EquationsAtoms are rearranged in a reaction, never created or destroyed, so every element must appear in equal numbers on both sides. Balance by adjusting the big numbers in front of formulae only — changing a subscript changes the substance itself.Lesson
- 5Reacting Mass CalculationsA balanced equation gives the mole ratio between substances — this is what stoichiometry means. Convert the known mass to moles, apply the ratio, then convert back to mass. It is exactly how a manufacturer works out how much raw material a batch of product needs.Experiment
- 6Limiting Reactants and Percentage YieldThe limiting reactant runs out first and caps how much product can form; the other is in excess. Real yields fall short of theoretical because of side reactions, losses in transfer and reversible steps. Percentage yield is actual divided by theoretical, times 100.Experiment
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