Q: What is the percent yield if the theoretical yield of a reaction is 10.0 g and the actual yield is 8.0 g?

$$\frac{8.0}{10.0} \times 100 = 80\%$$

Q: Which of the following equations correctly represents the percent yield formula?

$$\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100$$

Question 1

Which of the following best describes the greenhouse effect and its role in Earth's climate?

Accepted Answer

It allows sunlight to enter the atmosphere, warms Earth's surface, and prevents some heat from escaping.

Question 2

Which of the following is a combustion reaction?

Accepted Answer

A reaction in which a substance combines with oxygen to form one or more oxygen-containing compounds and emits heat.

Question 3

Which quantity must always be the same on both sides of a balanced chemical equation?

Accepted Answer

The number of atoms of each kind

Question 4

Given the balanced equation for the combustion of methane: $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, if you start with 5 molecules of $$\mathrm{CH_4$}$$ and 8 molecules of $$\mathrm{O_2$}$$, what is the limiting reactant?

Accepted Answer

$$\mathrm{O_2$}$$

Question 5

Which of the following best defines the theoretical yield in a chemical reaction?

Accepted Answer

The maximum amount of product that can be made based on the amount of limiting reactant.

Question 6

A reaction mixture contains 42.5 g of magnesium and 33.8 g of oxygen. Which is the limiting reactant?

Accepted Answer

Oxygen

Question 7

What is the percent yield if the theoretical yield of a reaction is 10.0 g and the actual yield is 8.0 g?

Accepted Answer

$$\frac{8.0}{10.0} 	imes 100 = 80\%$$

Question 8

Which of the following statements about limiting reactants is correct?

Accepted Answer

The limiting reactant is completely consumed in the reaction.

Question 9

If 2 moles of octane ($$\mathrm{C_8H_{18}}) $$react with 25 moles of oxygen ($$\mathrm{O_2$}$$), how many moles of carbon dioxide ($$\mathrm{CO_2$}) $$are produced according to the balanced equation: $$2\mathrm{C_8H_{18}} + 25\mathrm{O_2$} \rightarrow 16\mathrm{CO_2$} + 18\mathrm{H_2O}$$?

Accepted Answer

16 moles

Question 10

Which of the following is a correct description of a combustion reaction involving ethanol ($$\mathrm{C_2H_5OH}$$)?

Accepted Answer

$$\mathrm{C_2H_5OH} + 3O_2 \rightarrow 2CO_2 + 3H_2O$$

Question 11

Which of the following best describes the role of stoichiometry in chemical reactions?

Accepted Answer

It relates the amounts of reactants and products using the coefficients of a balanced chemical equation.

Question 12

A student burns 22.0 moles of octane ($$\mathrm{C_8H_{18}}). $$How many moles of $$\mathrm{CO_2$}$$ are produced? (Use the balanced equation: $$2\mathrm{C_8H_{18}} + 25\mathrm{O_2$} \rightarrow 16\mathrm{CO_2$} + 18\mathrm{H_2O})$$

Accepted Answer

176 moles

Question 13

Which of the following is true about excess reactants in a chemical reaction?

Accepted Answer

They are present in a quantity greater than required to react with the limiting reactant.

Question 14

Which of the following equations correctly represents the percent yield formula?

Accepted Answer

$$	ext{Percent Yield} = \frac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100$$

Question 15

Which of the following is a real-world consequence of the combustion of fossil fuels?

Accepted Answer

Increased atmospheric $$\mathrm{CO_2$}$$ levels, contributing to global warming.

Question 16

Which of the following reactions is most likely to be vigorous and exothermic?

Accepted Answer

Reaction of sodium with water.

Question 17

If 5 mol of $$\mathrm{NO_2$}$$ and 1 mol of $$\mathrm{H_2O}$$ react completely according to the equation $$3\mathrm{NO_2$} + \mathrm{H_2O} \rightarrow 2\mathrm{$$HNO_3$$} + \mathrm{NO}$$, how many moles of the reactant in excess remain?

Accepted Answer

2 mol

Question 18

Which of the following best describes the reaction between halogens and metals?

Accepted Answer

They form metal halides.

Question 19

Which of the following is NOT a characteristic of a combustion reaction?

Accepted Answer

It always produces a metal halide.

Chapter 4: Chemical Reactions and Chemical Quantities – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards