Solubility, Stoichiometry and Non-stoichiometry

The unspoken word of chemistry: Non-stoichiometric. Stoichiometry and non-stoichiometry are concepts that combine to make a solution that does not have to be difficult to understand.

Does Alka-Seltzer Tell the Truth? A lab activity with a video pre-lab assigment

The lab activity shared here is a simple experiment where students use stoichiometric principles to experimentally determine the amount of sodium bicarbonate in an Alka-Seltzer tablet. Novice students tend to find stoichiometric calculations difficult, so practicing the calculations on a pre-lab assignment boosts their confidence and ultimately leads to more successful labs. The Asynchronous Video Pre-Lab Assignment shared here demonstrates the procedure and the calculations required in the experiment.

Airbag challenge

In the “Airbag challenge” the students are tasked with developing a safe airbag for a car company. This formative assessment explores students’ thinking about the question “How can chemical changes be controlled?” The central concept in this challenge is the application is stoichiometry. Students are expected to use the numbers of moles of reactant consumed or product formed in a balanced chemical equation and to determine the change in the number of moles of any other reactant and product. Students need to use molar mass to convert mass of a reactant or product to moles for use in stoichiometric calculations or to convert moles from stoichiometric calculations to mass. Students use the ideal gas law equation to determine the numbers of moles in a sample of gas not at standard conditions.