This unit is not arranged as a traditional stoichiometry unit. Rather than beginning by stating the law of conservation of mass to students, it begins with an inquiry lab for students to discover that law. All quantities in this lab will be measured in grams. This will lead to a discussion of grams versus moles -- when each unit is appropriate and why. After students have developed this basic understanding, they will be presented with an in-class lab demonstration and subsequent simulation involving limiting reactants. Limiting reactants will be used to help students understand the most efficient ratios needed in a chemical equation that will produce maximum product. Students use this same logic and apply it in order to balance chemical equations.

Gapless Explanation of Anchoring Phenomenon (combination of Stoichiometry Part 1 & Part 2)

Can carbonation be introduced into a beverage without a gadget such as a sodastream? (A sodastream carbonates beverages by bubbling carbon dioxide directly into a beverage.) To carbonate a beverage in the classroom, two solid chemicals are mixed together to create the gaseous carbon dioxide, but this example reaction is not the only one that will produce carbon dioxide.

The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. Mass simply rearranges itself to form products. Thus, whatever mass we introduce as a reactant or reactants of a chemical reaction we will see that form the product or products. Quantities of solid chemicals in the laboratory are measured in grams. However, 1 gram of different chemicals or compounds does not contain the same number of atoms/particle units. The counting unit the mole is necessary to relate chemical compounds in an overall equation to each other and make sure amounts are comparable. One mole of a chemical or compound always contains the same number of atoms/particle units. Moles are also used to determine concentrations of aqueous solutions. Concentration is expressed as molarity (M) which is the number of moles of solute per liter of solution.

Reactant amounts in a chemical reaction should produce the maximum amount of desired product possible without leaving any excess reactants. Different reactants and products can only be compared if those amounts are in moles. The correct molar ratio for a chemical reaction is the ratio that will produce the maximum amount of product without any reactant going to waste. If an excess reactant remains after a chemical reaction occurs, then that ratio is not the correct one. Molar relationships lead to the idea of balancing equations. A balanced equation represents the correct molar ratio for an overall chemical reaction equation. When an equation is balanced, the same number of atoms (for a specific element) should be represented on the reactants and products side of the equation. A balanced equation represents atoms, but as the ratio of moles to atoms is the same for all elements, a balanced equation also represents moles.

If reactant quantities for a balanced chemical reaction are known, the theoretical yield of each product can be determined using dimensional analysis to complete stoichiometry calculations. In addition to determining theoretical yields, a limiting reactant and any amount of excess reactant can also be identified. This process can be applied and utilized to determine specific amounts of citric acid and baking soda that should be combined in a solution of Kool-Aid and sugar to carbonate the beverage and create soda pop. If incorrect amounts of either reactant are used, there will be excess reactant remaining which will affect the taste of the beverage.

Unit designed by Carole Namowicz a teacher at Lindblom.