Stoichiometry

Learning Objectives

  • The application of mass-mass stoichiometry to gravimetric analysis to determine the mass of a salt in a water sample

  • Volume-volume stoichiometry (solutions only)

Summary Notes

The topic of stoichiometry is covered across the following topics:

  • Analysis of Salts in Water

  • Analysis of Organic Compounds

  • Analysis of Acids and Bases

As such, a compilation has been made to summarise the main idea of this topic.

Notes for the topics mentioned will be progressively added.

Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions.

These quantities can be amount (mass or moles), concentration, volume or even enthalpy.

Gravimetric analysis is the analysis of masses. Volumetric analysis is the analysis of volumes.

Gravimetric analysis is usually used during a precipitation reaction. Volumetric analysis is often used with a titration.

The main differences between the two analysis can be found here.

Notes on titrations can be found in the Analysis of Acids and Bases topic.

The best method for solving stoichiometry questions is by using a 7 (sometimes 5 if steps 4, 5 and 6 are combined) step process.

Eg. A 10.0g sample of magnesium carbonate (MgCO₃) is added to an excess amount of hydrochloric acid (HCl) and allowed to completely react. Calculate the mass of CO₂ produced.

Steps 3 and 7 will change depending on the quantities provided and desired.

Another important equation that can be used in steps 3 and 7 is:

This is especially used when volume or concentration is given or desired.

Video to help build your understanding

Worked Example of Mass-to-mass Stoichiometry

Worked Example of Volumetric Analysis Stoichiometry

Practice Material

Stoichiometry Workbook and Solutions

Gravimetric Analysis Quiz

Volumetric Analysis Calculations

Stoichiometry Calculation Quiz

Teacher's Tips:

You can never go wrong with the 7 step stoichiometry method.

Always organise your solutions clearly from left to right. This helps the examiner easily determine if you get any consequential marks. Messy working out tends to not get as many marks as it can be difficult to decipher your work.