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Product 12910

By: The Flinn Staff

With the Determining a Balanced Chemical Equation Laboratory Kit, solutions of the reactants are prepared with known concentrations. Solutions are mixed, using different ratios of reactants. Then the amount of heat liberated is measured.

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Stoichiometry! A word as strange to some students as the concept it defines. A balanced chemical equation gives the mole ratio of reactants and products for a chemical reaction. When chemical formulas are known, it is relatively easy to determine the mole ratios. When formulas are not known, students must apply experimentation to solve for these ratios. This experiment uses the method of continuous variation. First, solutions of the reactants are prepared with known concentrations. Solutions are then mixed a number of times using different volume ratios of reactants. Third, a property of the reaction—in this case, heat liberated—is measured. Students use the data to graph the mole ratio versus change in temperature. The intersection of the lines drawn through the ascending and descending data points gives the correct mole ratio for the reaction. Includes reproducible student handouts, detailed background information, Teacher Notes with sample data and answers to questions, and all chemicals and consumable supplies needed to perform the lab. Complete for 30 students working in pairs. Perform this experiment in a fume hood or well-ventilated lab.

Correlation to Next Generation Science Standards (NGSS)

Science & Engineering Practices

Asking questions and defining problems
Planning and carrying out investigations
Analyzing and interpreting data
Using mathematics and computational thinking
Engaging in argument from evidence

Disciplinary Core Ideas

MS-PS1.B: Chemical Reactions
HS-PS1.B: Chemical Reactions

Crosscutting Concepts

Systems and system models
Scale, proportion, and quantity

Performance Expectations

HS-PS1-3: Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.