2 Atoms, molecules and stoichiometryAS Level

2.4 Reacting masses and volumes (of solutions and gases)

1 of 1 objectives have lessons · 0 studied · 0 secure

Lessons

Reacting masses: cross the mole bridgeWhy balanced equations work in moles, not grams, and the three-step method for turning a mass of one substance into the mass of another. 5 min, not started
Percentage yield: where did my product go?Theoretical yield, actual yield and percentage yield, why real reactions fall short of 100%, and how to work backwards from a target mass. 4 min, not started
Gas volumes: every mole gets 24 dm³Why one mole of any gas fills the same volume, how to use the molar volume from the Data Booklet, and why gas volumes react in the same ratio as moles. 5 min, not started
Burning hydrocarbons: the gas-volume detectiveUsing gas volumes from burning a hydrocarbon to find oxygen used, carbon dioxide made and, from the clues left behind, the hydrocarbon's formula. 5 min, not started
Concentration: how crowded is your solution?Concentration in mol dm⁻³ and g dm⁻³, the n = cV toolkit with the cm³ to dm³ trap, concentrations of ions, and dilution. 5 min, not started
Titration calculations, step by stepHow to pick concordant titres, the four-step route from a titre to an unknown concentration, and how to scale up from a portion to the whole flask. 5 min, not started
Limiting and excess reagentsHow to find which reactant runs out first, use it to calculate the product, and work out how much of the excess reactant is left over. 5 min, not started
From numbers to equations: deducing stoichiometryHow to work backwards from measured masses, gas volumes, titres or a break-point graph to the mole ratio, and so to the balanced equation. 5 min, not started

Syllabus objectives

1 objective

What Cambridge says you should be able to do, in our words. Codes are the topic number plus the objective’s position.

2.4.1

Perform calculations using the mole concept involving: (a) reacting masses (from formulas and equations), including percentage yield calculations; (b) volumes of gases (e.g. in the burning of hydrocarbons); (c) volumes and concentrations of solutions; (d) limiting reagent and excess reagent; and (e) deduce stoichiometric relationships from calculations such as those in (a)–(d).

Answers should reflect the number of significant figures given or asked for in the question. When rounding up or down, significant figures should be neither lost unnecessarily nor used beyond what is justified (see also the Mathematical requirements section of the syllabus).

Taught in: Burning hydrocarbons: the gas-volume detective, Concentration: how crowded is your solution?, From numbers to equations: deducing stoichiometry, Reacting masses: cross the mole bridge, Gas volumes: every mole gets 24 dm³, Limiting and excess reagents, Percentage yield: where did my product go?, Titration calculations, step by step · 49 questions