Chemistry Module 8 Test Review

Questions and Answers

Define stoichiometry and explain why it is such a useful tool for scientists.

Stoichiometry is the method used to relate the quantities of substances in chemical equations. It is useful because with the quantities of just one substance in the equation, we can learn something about the quantities of all other substances in that equation.

What is a limiting reactant and why is it important?

A limiting reactant is a reactant that limits the amount of a product that can be formed in the chemical equation. It is important because it determines the amount of products produced.

What are excess reactants?

Excess reactants are the reactants in a chemical reaction that remain when a reaction stops when the limiting reactant is completely consumed.

What are stoichiometric coefficients?

Stoichiometric coefficients are the numbers that appear to the left of each substance in the equation. Signup and view all the answers

What do stoichiometric coefficients do?

They provide a way of converting from the number of moles of one substance in the equation to the number of moles in another substance in the equation. Signup and view all the answers

What is Gay-Lussac's Law and how is it used?

Gay-Lussac's Law explains that stoichiometric coefficients in a chemical equation relate the volumes of gases in the equation, as well as the number of moles. It is used to relate the quantities of gaseous substances in a chemical equation if they are given in volume units. Signup and view all the answers

What is a molecular formula?

A molecular formula is a chemical formula that provides the number of each type of atom in a molecule. Signup and view all the answers

What is an empirical formula?

An empirical formula is a chemical formula that provides a simple whole-number ratio for atoms in a molecule. Signup and view all the answers

What is molar mass?

Molar mass is the mass of one mole of a given compound. Signup and view all the answers

If a stoichiometry problem gives you the quantity of a substance in grams, what is the first thing you must do to solve the problem? Why?

Convert to moles. It must be done because the ratio from the balanced equation is in moles. Signup and view all the answers

What is the difference between molecular formulas and empirical formulas?

Molecular formulas provide the exact number of each type of atom in the molecule, while empirical formulas provide only a simple, whole-number ratio of atoms in the molecule. Signup and view all the answers

Study Notes

Stoichiometry

Stoichiometry relates quantities of substances in chemical equations.
Allows determination of all substance quantities from one known quantity.

Limiting Reactant

A limiting reactant is the substance that limits product formation.
Crucial for calculating the maximum products obtainable from a reaction.

Excess Reactants

Excess reactants are substances remaining after the limiting reactant is consumed.
They do not affect the amount of product formed once the reaction stops.

Stoichiometric Coefficients

Stoichiometric coefficients are numbers indicating the ratio of substances in a chemical equation.
Key for converting moles of one substance to moles of another.

Gay-Lussac's Law

Relates the volumes of gases in a chemical reaction using stoichiometric coefficients.
Useful for understanding the relationships when quantities are expressed in volume.

Molecular Formula

A molecular formula shows the exact number of each type of atom in a molecule.
Provides complete information about the composition of a substance.

Empirical Formula

An empirical formula represents the simplest whole-number ratio of atoms in a molecule.
Does not give specific atom counts but rather a ratio.

Molar Mass

Molar mass is the mass of one mole of a compound.
Acts as a conversion rate from grams to the number of molecules.

Initial Steps in Stoichiometry Problems

First step is to convert grams to moles for stoichiometry problems.
This is necessary as the balanced equation’s ratios are based on moles.

Comparison of Molecular and Empirical Formulas

Molecular formulas give exact counts of atoms in a molecule, while empirical formulas provide simple ratios.
Important distinction for determining molecular structure versus composition.

Description

Prepare for your Chemistry Module 8 exam with these flashcards. This review covers key concepts such as stoichiometry and limiting reactants, highlighting their importance in chemical equations and reactions. Perfect for reinforcing your understanding of these foundational topics.