AP Chemistry Unit 4.5: Stoichiometry

Practice AP Chemistry Unit 4.5 questions on using balanced reactions to calculate amounts, identify limiting reactants, and connect stoichiometry with solution and gas data.

Exam points

Use equilibrium, acid–base, and solubility models to predict pH, species, precipitation, and reaction direction.
Calculate concentrations, Ka/Kb, Ksp, and titration quantities from balanced equations and experimental data.
Interpret molecular and particulate evidence to explain buffers, common-ion effects, and solution composition.

Covered syllabus points

4.5.A—Explain changes in the amounts of reactants and products based on the balanced reaction equation for a chemical…

[Maximum number: 1]

Answer the following questions about ascorbic acid (vitamin C).

A student combusts a sample of ascorbic acid, $\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}_{x}$ , to determine its chemical

composition. The only products of the reaction are 0.2400 mol of $\mathrm{CO}_{2}$ and 2.883 g of $\mathrm{H}_{2} \mathrm{O}$ .

Calculate the number of moles of $\mathrm{H}_{2} \mathrm{O}$ produced.

A (i) For the correct calculated value:

$2.883 \mathrm{~g} \mathrm{H}_{2} \mathrm{O} \times \frac{1 \mathrm{~mol} \mathrm{H}_{2} \mathrm{O}}{18.02 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}}=0.1600 \mathrm{~mol} \mathrm{H}_{2} \mathrm{O}$

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Covered syllabus points

4.5 Stoichiometry question 1