Q: How many atoms are present in 3.0 g of copper (Cu)? (Molar mass of Cu = 63.5 g/mol, Avogadro's number = $$6.02 \times 10$$^{23}$$ atoms/mol)

$$2.85 \times 10$$^{22}$$ atoms$

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

$$\displaystyle \frac{\text{actual yield}}{\text{theoretical yield}} \times 100$$

Q: Which of the following is the correct definition of Avogadro's number?

The number of particles in one mole, $$6.02 \times 10$$^{23}$$.

Question 1

Which of the following best explains why we balance chemical equations by adjusting coefficients rather than changing subscripts?

Accepted Answer

Changing subscripts creates new substances with different properties, while coefficients only change the amount of each substance.

Question 2

Which of the following is the correct balanced equation for the combustion of propane, $$\mathrm{C_3H_8}$$, in oxygen?

Accepted Answer

$$\mathrm{C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(g)}$$

Question 3

A sample of glucose ($$\mathrm{C_6H_{12}O_6$}) $$weighs 18.0 g. How many moles of glucose are present in the sample? (Molar mass of glucose = 180.0 g/mol)

Accepted Answer

$$0.10$$ mol

Question 4

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

Accepted Answer

$$\mathrm{C_7H_7NO_2}$$

Question 5

A reaction has a theoretical yield of 10.0 g, but only 7.5 g of product is actually obtained. What is the percent yield?

Accepted Answer

$$75\%$$

Question 6

Which of the following statements about limiting reactants is correct?

Accepted Answer

The limiting reactant is completely consumed first and determines the maximum amount of product formed.

Question 7

Calculate the formula weight of sulfuric acid, $$\mathrm{H_2SO_4}$$, using the following atomic weights: H = 1.0 amu, S = 32.1 amu, O = 16.0 amu.

Accepted Answer

$$98.1$$ amu

Question 8

Which of the following best describes a decomposition reaction?

Accepted Answer

A single substance breaks down into two or more substances.

Question 9

How many atoms are present in 3.0 g of copper (Cu)? (Molar mass of Cu = 63.5 g/mol, Avogadro's number = $$6.02 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$2.85 	imes 10$$^{22}$$ atoms$

Question 10

Which of the following is the correct percent composition of carbon in glucose ($$\mathrm{C_6H_{12}O_6$}$$)? (Molar mass = 180.0 g/mol)

Accepted Answer

$$40.0\%$$

Question 11

A compound has an empirical formula of CH and a molar mass of 78 g/mol. What is its molecular formula?

Accepted Answer

$$\mathrm{C_6H_6}$$

Question 12

Which of the following is a correct statement about combustion reactions?

Accepted Answer

Combustion reactions most often involve oxygen as a reactant and produce a flame.

Question 13

If 1.00 g of glucose ($$\mathrm{C_6H_{12}O_6$}) is $$completely combusted, how many grams of water ($$\mathrm{H_2O}) $$can be produced? (Molar mass of glucose = 180.0 g/mol, molar mass of $$\mathrm{H_2O} = 18.0 g/$$mol, balanced equation: $$\mathrm{C_6H_{12}O_6$} + 6O_2 \rightarrow 6CO_2 + 6H_2O)$$

Accepted Answer

$$0.600 g$$

Question 14

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

Accepted Answer

$$\displaystyle \frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100$$

Question 15

Which of the following is true about the coefficients in a balanced chemical equation?

Accepted Answer

They indicate the relative numbers of moles and molecules of reactants and products.

Question 16

A metal carbonate is heated and decomposes to form a metal oxide and carbon dioxide. Which of the following is the correct balanced equation for the decomposition of calcium carbonate?

Accepted Answer

$$\mathrm{$$CaCO_3$$(s) \rightarrow CaO(s) + CO_2$(g)}$$

Question 17

Which of the following is the correct definition of Avogadro's number?

Accepted Answer

The number of particles in one mole, $$6.02 	imes 10$$^{23}$$.

Question 18

Which of the following steps is NOT part of determining an empirical formula from percent composition?

Accepted Answer

Divide the percent composition by Avogadro's number.

Question 19

Which of the following best describes a combination reaction?

Accepted Answer

Two or more reactants combine to form a single product.

Chapter 3: Chemical Reactions and Reaction Stoichiometry – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards