Chemical Equations, Stoichiometry, and Yield Calculations

A set of flashcards covering definitions, formulas, and example problems related to chemical equations, stoichiometry, limiting reactants, yields, and atom economy.

What is a chemical equation?

A symbolic representation of a chemical reaction showing reactants and products, their physical states, and their molar ratios.

Why must chemical equations be balanced?

To satisfy the law of conservation of mass, because atoms cannot be created or destroyed in a chemical reaction.

What do the state symbols (s), (l), (g), and (aq) signify in a chemical equation?

(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water).

List the basic steps for balancing a chemical equation.

1. Write correct formulae for all reactants and products. 2. Count the atoms of each element on both sides. 3. Balance using the smallest whole-number coefficients. 4. Recheck the equation to confirm atom balance.

Provide the balanced form of the reaction H₂ + O₂ → H₂O.

2H₂ + O₂ → 2H₂O

What is a mole ratio in the context of a balanced chemical equation?

The ratio of the amounts (in moles) of substances involved, derived directly from the stoichiometric coefficients in the balanced equation.

In 2H₂ + O₂ → 2H₂O, what is the mole ratio of H₂ to H₂O?

2 : 2, which simplifies to 1 : 1.

How do you calculate the mass of a substance from a chemical equation?

Use mole ratios from the balanced equation and apply Mass = Moles × Molar Mass.

What is the formula for calculating moles from a given mass?

Moles = Mass ÷ Molar Mass.

Define a limiting reactant.

The reactant that is completely consumed first, thus limiting the amount of product that can form.

What is theoretical yield?

The calculated maximum possible amount of product that can be formed from given reactants.

State the formula for percentage yield.

Percentage yield = (Actual yield ÷ Theoretical yield) × 100.

State the formula for atom economy.

Atom economy = (Mr of desired product ÷ Total Mr of all products) × 100.

Why is a high atom economy desirable in chemical processes?

It minimizes waste and enhances sustainability by making better use of reactant atoms.

According to the provided example, what mass of water is produced when 4.00 g of hydrogen reacts with oxygen?

36.0 g of H₂O.

In the example reaction Ca + 2HCl → CaCl₂ + H₂, what mass of CaCl₂ is formed from 5.00 g of calcium (with excess HCl)?

13.88 g of CaCl₂.