Chemistry Chapter 12: Stoichiometry Flashcards

Questions and Answers

What is stoichiometry?

The calculation of quantities in chemical reactions is a subject of chemistry.

What is a mole ratio?

A conversion factor derived from coefficients of a balanced chemical equation interpreted in terms of moles.

What is a limiting reagent?

The reagent that determines the amount of product that can be formed by a reaction.

What is an excess reagent?

The reactant not completely used up in a reaction. Signup and view all the answers

What is theoretical yield?

The maximum amount of product that could be formed from given amounts of reactants. Signup and view all the answers

What is actual yield?

The amount of product that actually forms when the reaction is carried out in the laboratory. Signup and view all the answers

What is percent yield?

The ratio of the actual yield to the theoretical yield expressed as a percent. Signup and view all the answers

How do chemists use balanced chemical equations?

To calculate how much reactant is needed or product is formed in a reaction. Signup and view all the answers

What quantities can you interpret from a balanced chemical equation?

Numbers of atoms, molecules, or moles; mass and volume. Signup and view all the answers

In a chemical reaction, mass is conserved.

True Signup and view all the answers

In mole to mole conversions: Amount of given substance A in moles multiplied by mole ratio from balanced equation equals amount of unknown substance B in moles. A (in moles) x ____ = B (in moles)

mole ratio Signup and view all the answers

In mole to mass conversions: Amount of given substance A in moles multiplied by #1: Mole ratio from balanced equation multiplied by #2 Molar Mass from periodic table equals amount of unknown substance B in grams. A (in moles) x #1 x #2 = B (in grams)

molar mass Signup and view all the answers

In mass to mole conversions: Amount of given substance A in grams multiplied by #2 Molar mass from periodic table multiplied by #1 Mole ratio from balanced equation equals amount of unknown substance B in moles. A (in grams) x #2 x #1 = B (in moles)

mole ratio Signup and view all the answers

In mass to mass conversions: Amount of given substance A in grams multiplied by #2 Molar mass from periodic table multiplied by #1 Mole ratio from balanced equation multiplied by #3 Molar mass from periodic table equals amount of unknown substance B in grams. A (in grams) x #2 x #1 x #3 = B (in grams)

molar mass Signup and view all the answers

How do you convert grams of substance A to molecules of substance B?

Grams A → Molecules B, Molecules A → Grams B. Signup and view all the answers

Given the reaction N₂ + 3F₂ → 2NF₃, how many molecules of nitrogen are needed to produce 3.17g of nitrogen trifluoride?

1.33 x 10²² molecules N₂ Signup and view all the answers

Given the reaction N₂(g) + 3H₂(g) → 2NH₃ (g), if 14.5 liters of hydrogen gas is used, how many liters of ammonia would be produced?

9.67 L NH₃ Signup and view all the answers

Identify the limiting and excess reactants in the reaction Mg + 2H₂O → Mg(OH)₂ + H₂ when 16.2 g Mg are reacted with 12.0g H₂O.

Limiting: 12.0 g H₂O; Excess: 16.2 g Mg Signup and view all the answers

What does the percent yield of a reaction measure?

The efficiency of a reaction carried out in the laboratory. Signup and view all the answers

Calculate the percent yield given that the actual yield is 46.3 g KCl and the theoretical yield is 49.4 g KCl.

% yield = 46.3 g KCl / 49.4 g KCl x 100 Signup and view all the answers

Study Notes

Stoichiometry Basics

Stoichiometry involves calculating quantities in chemical reactions.
A mole ratio is derived from the coefficients in a balanced chemical equation, used as a conversion factor.

Key Concepts

The limiting reagent is the reactant that limits the amount of product formed in a reaction.
An excess reagent is the reactant that remains unreacted after the reaction completes.
The theoretical yield represents the maximum possible product yield from given reactants, while actual yield is the product amount obtained in practice.
Percent yield is the ratio of actual yield to theoretical yield, expressed as a percentage.

Application of Balanced Equations

Chemists utilize balanced chemical equations for determining reactant quantities needed and product amounts generated.
A balanced equation provides insight into numbers of atoms, molecules, or moles along with their mass and volume conversions.

Conservation of Mass Principle

In chemical reactions, mass conservation means that matter cannot be created or destroyed.

Conversion Processes

Mole to Mole: Use mole ratios to convert amount of one substance in moles to another.
Mole to Mass: Multiply moles by mole ratio and then by the molar mass to find mass in grams.
Mass to Mole: Use grams multiplied by molar mass and mole ratio to determine moles.
Mass to Mass: Combine grams, mole ratios, and molar masses to convert between masses of two substances.
Mass to Molecules: Convert grams to molecules or vice versa.

Examples

Mass to Molecules Conversion: To find the number of molecules of nitrogen needed for 3.17g of nitrogen trifluoride, the result is 1.33 x 10²² molecules of N₂.
Volume to Volume Conversion Example: From 14.5 L of hydrogen gas, 9.67 L of ammonia can be produced under STP conditions.

Limiting Reactants Example

Given the reaction Mg + 2H₂O → Mg(OH)₂ + H₂, with 16.2g of Mg and 12.0g of H₂O:
- Limiting reagent: 12.0g H₂O
- Excess reagent: 16.2g Mg

Percent Yield Calculation

Percent yield measures a reaction's efficiency:
- Given actual yield of 46.3g KCl and theoretical yield of 49.4g KCl, the calculation is:
- % yield = (46.3g / 49.4g) x 100.

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Test your knowledge of stoichiometry with these flashcards that cover key concepts such as mole ratio, limiting reagent, and more. Perfect for students looking to enhance their understanding of chemical quantities and reactions.