Chemistry Chapter 9 Stoichiometry Quiz

Questions and Answers

Explain the concept of mole ratio as used in reaction stoichiometry problems. What is the source of this ratio?

Mole ratio is used as conversion factors from moles of a reactant to another. The ratio is also used to show the balanced equation of the reaction occurring.

What is molar mass?

The mass in grams of one mole of a substance.

What is the role of molar mass in reaction stoichiometry?

It is used as a conversion factor when the mass of a given substance is divided by its amount of substance.

Distinguish between ideal and real stoichiometric calculations.

Ideal calculations tell the maximum possible amount of products that can be formed under perfect conditions. Real calculations are the actual amount available to form in the actual reaction. Signup and view all the answers

Distinguish between the limiting reactant and the excess reactant in a chemical reaction.

The limiting reactant is the reactant that controls the amount of product formed in a chemical reaction. The substance not used up completely in a reaction is the excess reactant. Signup and view all the answers

Distinguish between the theoretical yield and actual yield in stoichiometric calculations.

Theoretical yield is the maximum amount of product that can be produced from a given amount of reactant. Actual yield is the amount of product actually yielded by the reaction under actual conditions. Signup and view all the answers

How does the value of the theoretical yield generally compare with the value of the actual yield?

The theoretical yield is generally more than the actual yield. Signup and view all the answers

What is the percentage yield of a reaction?

The ratio of the actual yield to the theoretical yield multiplied by 100. Signup and view all the answers

Why are actual yields usually less than calculated theoretical yields?

<ol> <li>Sometimes the reaction does not go to completion. 2. Sometimes impure reactants are reacting. 3. There can be competing side reactions. 4. Products can be lost when purified.</li> </ol> Signup and view all the answers

Explain the stoichiometry of blowing air on a smoldering fire to keep the coals burning.

Blowing air on coals blows away the carbon dioxide surrounding the coals and adds oxygen to the fire, which keeps it burning. Signup and view all the answers

Reaction stoichiometry involves the ____ between reactants and products in a chemical reaction.

mass relationships Signup and view all the answers

Relating one substance to another requires expressing the amount of each substance in ____.

moles Signup and view all the answers

A ____ is the conversion factor that relates the amount in moles of any two substances in a chemical reaction.

mole ratio Signup and view all the answers

The mole ratio is derived from...

The balanced chemical equation. Signup and view all the answers

Amount of substance is expressed in ____.

moles Signup and view all the answers

Mass of a substance is expressed by using mass units such as , , or .

grams, kilograms, milligrams Signup and view all the answers

Mass and amount of substance are _ whereas moles and grams are _

quantities, units Signup and view all the answers

A _____ is necessary to solve any stoichiometric problem.

balanced chemical equation Signup and view all the answers

In an ideal stoichiometric calculation, the mass or the amount of any reactant or product can be calculated if...

the balanced chemical equation and the mass or amount of any other reactant or product is known. Signup and view all the answers

In actual reactions, the reactants may be present in proportions that differ from stoichiometric proportions required for a complete reaction in which all of each reactant is converted to product. This produces a ____.

limiting and excess reactant Signup and view all the answers

The _____ controls the maximum possible amount of product formed.

limiting reactant Signup and view all the answers

For many reactions, the quantity of a product is ____ than the theoretical maximum for that product.

less Signup and view all the answers

____ shows the relationship between the theoretical yield and the actual yield for the product of a reaction.

Percentage yield Signup and view all the answers

Study Notes

Mole Ratio and Molar Mass

Mole ratio serves as a conversion factor from one reactant to another, reflecting the balanced equation of a chemical reaction.
Molar mass is defined as the mass in grams of one mole of a substance and is crucial in stoichiometric calculations.

Role of Molar Mass in Stoichiometry

Molar mass acts as a conversion factor when determining the relationship between mass and moles of a substance.

Ideal vs. Real Stoichiometric Calculations

Ideal calculations predict the maximum amount of products possible under perfect conditions.
Real calculations consider the actual yield that can be attained during a reaction.

Limiting and Excess Reactants

The limiting reactant dictates the maximum amount of product that can be formed in a chemical reaction.
The excess reactant is the substance that remains unconsumed after the reaction.

Theoretical Yield vs. Actual Yield

Theoretical yield represents the maximum possible product obtainable, while actual yield refers to the amount actually produced during the reaction.
Generally, theoretical yield exceeds actual yield.

Percentage Yield

Percentage yield is calculated as the ratio of actual yield to theoretical yield, multiplied by 100.

Reasons for Lower Actual Yields

Common factors for actual yields falling short of theoretical yield include incomplete reactions, impurities in reactants, competing side reactions, and loss of products during purification.

Stoichiometric Concepts in Reactions

Stoichiometry deals with mass relationships between reactants and products.
Relating substances requires expressing their amounts in moles.

Conversion Factors and Relationships

The mole ratio is derived from the balanced chemical equation and serves as the conversion factor connecting moles of two substances.
Balanced chemical equations are essential for solving stoichiometric problems and calculating mass or amount of reactants and products.

Practical Implications of Stoichiometry

In real reactions, reactants may not be present in stoichiometric proportions, leading to limiting and excess reactant situations.
The limiting reactant ultimately controls the maximum potential yield of products.

Summary of Yields

In many cases, the quantity of product produced is inferior to the theoretical maximum.
Percentage yield reflects the efficiency of a reaction by showing the relationship between theoretical and actual yields.

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Description

Test your understanding of stoichiometry with this review of Chapter 9. This quiz covers concepts like mole ratios and molar mass, crucial for solving reaction problems. Use these flashcards to reinforce your knowledge and prepare for your examinations.