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The Mole Ratio Stoichiometry Chemical Demonstration Kit promotes great critical-thinking and determining balanced equations. The method of continuous variation is presented to students for an interesting oxidation–reduction reaction.

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Determine a balanced chemical equation when you only know the formulas of the reactants using the method of continuous variation. Mix solutions of sodium hyopchlorite and sodium thiosulfate in various volume and mole ratios, with the total number of moles of reactants held constant. The amount of heat released in the exothermic reaction is directly proportional to the amount of product formed. The maximum temperature change is produced at the optimum mole ratio of reactants. Students plot temperature versus the volume ratios to determine the mole ratio and identify the products of the overall reaction. Great critical-thinking demonstration!

Concepts: Stoichiometry, mole ratio, oxidation–reduction, heat of reaction.
Time Required: 20 minutes
Note: Perform this demonstration in a fume hood or well-ventilated lab.

Correlation to Next Generation Science Standards (NGSS)

Science & Engineering Practices

Analyzing and interpreting data
Using mathematics and computational thinking

Disciplinary Core Ideas

MS-PS1.B: Chemical Reactions
MS-PS3.A: Definitions of Energy
HS-PS1.B: Chemical Reactions

Crosscutting Concepts

Patterns
Scale, proportion, and quantity
Energy and matter
Stability and change

Performance Expectations

HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.