Q: How many molecules are in 2.00 moles of $$\mathrm{CO}_2$$? (Avogadro's number $$= 6.022 \times 10$$^{23}$$ molecules/mol)

$$1.20 \times 10$$^{24}$$ molecules

Q: Which of the following is the correct formula for calculating percent yield?

$$\text{Percent yield} = \dfrac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$$

Question 1

Which statement best describes the Law of Conservation of Mass as it applies to chemical reactions?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 2

When balancing chemical equations, which of the following is a correct rule?

Accepted Answer

Only change the coefficients in front of compounds to balance the equation.

Question 3

Which of the following is a combination reaction?

Accepted Answer

$$\mathrm{Mg} (s) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{MgO} (s)$$

Question 4

Aqueous solutions are important in chemistry because:

Accepted Answer

They allow substances to dissolve and react in water, facilitating ion formation.

Question 5

What is the formula weight (FW) of sodium chloride ($$\mathrm{NaCl}$$)? (Atomic weights: Na = 23.0 amu, Cl = 35.5 amu)

Accepted Answer

$$58.5$$ amu

Question 6

Which of the following best describes a decomposition reaction?

Accepted Answer

A single compound breaks down into two or more substances.

Question 7

How many molecules are in 2.00 moles of $$\mathrm{CO}_2$$? (Avogadro's number $$= 6.022 	imes 10$$^{23}$$ molecules/mol)

Accepted Answer

$$1.20 	imes 10$$^{24}$$ molecules

Question 8

A sample contains 18.0 g of water ($$\mathrm{H}_2\mathrm{O}). $$How many moles of water are present? (Molar mass of $$\mathrm{H}_2\mathrm{O}$$ = $$18.0 g/$$mol)

Accepted Answer

$$1.0$$ mol

Question 9

Which of the following is the correct percent composition by mass of carbon in glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$)? (Atomic weights: C = 12.0, H = 1.0, O = 16.0)

Accepted Answer

$$40\%$$

Question 10

A hydrocarbon ($$\mathrm{C}_3\mathrm{H}_8) $$undergoes complete combustion. What are the products?

Accepted Answer

$$\mathrm{CO}_2$$ and $$\mathrm{H}_2\mathrm{O}$$

Question 11

If 1.00 mol of $$\mathrm{NaCl}$$ contains $$6.022 	imes 10$$^{23}$$ formula units, how many formula units are in 0.25 mol of $$\mathrm{NaCl}$$?

Accepted Answer

$$1.51 	imes 10$$^{23}$$

Question 12

Which of the following is the correct empirical formula for a compound containing 61.31% C, 5.14% H, 10.21% N, and 23.33% O by mass?

Accepted Answer

$$\mathrm{C}_7\mathrm{H}_7\mathrm{NO}_2$$

Question 13

In a reaction, 50.0 g of $$\mathrm{NaOH}$$ reacts with 50.0 g of $$\mathrm{HCl}. $$Which is the limiting reactant? (Molar masses: $$\mathrm{NaOH} = 40.0 g/$$mol, $$\mathrm{HCl} = 36.5 g/$$mol)

Accepted Answer

$$\mathrm{HCl}$$

Question 14

What is the percent yield if the theoretical yield of $$\mathrm{NaCl} is 71.05 g $$and the actual yield is 48.7 g?

Accepted Answer

$$68.5\%$$

Question 15

Which of the following best describes the role of coefficients in a balanced chemical equation?

Accepted Answer

They indicate the number of moles of each substance involved in the reaction.

Question 16

A student burns 0.500 g of a compound containing C, H, and O in excess oxygen. The combustion produces 1.10 g of $$\mathrm{CO}_2$$ and 0.450 g of $$\mathrm{H}_2\mathrm{O}. $$What is the mass of carbon in the original sample? (Molar mass: $$\mathrm{CO}_2 = 44.0 g/$$mol)

Accepted Answer

$$0.300 g$$

Question 17

Which of the following is the correct formula for calculating percent yield?

Accepted Answer

$$	ext{Percent yield} = \dfrac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100\%$$

Question 18

Which of the following is NOT required in a complete chemical equation?

Accepted Answer

The atomic weights of all elements involved.

Question 19

A student needs to convert 10.0 g of copper ($$\mathrm{Cu}) to $$atoms. Which sequence of conversions is correct?

Accepted Answer

grams $$\rightarrow$$ moles $$\rightarrow$$ atoms

Chapter 3 – Chemical Reactions and Reaction Stoichiometry: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards