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

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

Question 1

Which law is the foundation of stoichiometry and states that matter is neither created nor destroyed in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 2

Given the balanced equation $$\mathrm{CH_4$(g) + 2O_2(g) \rightarrow CO_2$(g) + 2H_2O(g)}$$, what is the total number of oxygen atoms on the reactant side?

Accepted Answer

4

Question 3

Why do we balance chemical equations by adding coefficients rather than changing subscripts?

Accepted Answer

Changing subscripts changes the identity and properties of the compound.

Question 4

Which of the following is a decomposition reaction?

Accepted Answer

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

Question 5

A sample of ethane ($$\mathrm{C_2H_6}) $$has a mass of 30.070 amu. What is the percent by mass of carbon in ethane?

Accepted Answer

79.89%

Question 6

Which of the following best describes Avogadro’s number?

Accepted Answer

The number of atoms or molecules in one mole of a substance

Question 7

If the empirical formula of a compound is CH and its molar mass is 78 g/mol, what is its molecular formula?

Accepted Answer

$$\mathrm{C_6H_6}$$

Question 8

A compound is found to contain 61.31% C, 5.14% H, 10.21% N, and 23.33% O by mass. What is the empirical formula?

Accepted Answer

$$\mathrm{C_7H_7NO_2}$$

Question 9

In a combustion analysis, a 1.00 g sample of a compound containing C, H, and O produces 1.47 g of $$\mathrm{CO_2$}$$ and 0.60 g of $$\mathrm{H_2O}. $$What is the mass of carbon in the sample? (Molar mass: $$\mathrm{CO_2$} = 44.01 g/$$mol, C = 12.01 g/mol)

Accepted Answer

0.401 g

Question 10

Which of the following statements about limiting reactants is correct?

Accepted Answer

The limiting reactant determines the maximum amount of product formed.

Question 11

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 12

How many grams of water can be produced from 1.00 g of glucose ($$\mathrm{C_6H_{12}O_6$}) $$according to the equation $$\mathrm{C_6H_{12}O_6$(s) + 6O_2(g) \rightarrow 6CO_2(g) + 6H_2O(l)}$$? (Molar mass of glucose = 180.16 g/mol, water = 18.02 g/mol)

Accepted Answer

0.600 g

Question 13

Which of the following is a combination reaction?

Accepted Answer

$$\mathrm{N_2$(g) + 3H_2(g) \rightarrow 2NH_3(g)}$$

Question 14

What is the molar mass of calcium chloride ($$\mathrm{$$CaCl_2$$}$$)? (Ca = 40.08 g/mol, Cl = 35.45 g/mol)

Accepted Answer

110.98 g/mol

Question 15

Which of the following best describes a combustion reaction?

Accepted Answer

A reaction in which a substance reacts with oxygen, releasing energy as heat and light.

Question 16

If 4.0 g of $$\mathrm{H_2$}$$ reacts with 32.0 g of $$\mathrm{O_2$} to $$form water, what is the total mass of water produced? (Assume complete reaction.)

Accepted Answer

36.0 g

Question 17

Which of the following is NOT a correct statement about ionic compounds?

Accepted Answer

Ionic compounds exist as discrete molecules.

Question 18

A student mixes 5.0 g of $$\mathrm{H_2$}$$ with 10.0 g of $$\mathrm{O_2$} in a $$reaction to form water. Which is the limiting reactant? (Molar mass: $$\mathrm{H_2$} = 2.02 g/$$mol, $$\mathrm{O_2$} = 32.00 g/$$mol)

Accepted Answer

$$\mathrm{H_2$}$$

Question 19

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

Accepted Answer

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

Chemical Reactions and Reaction Stoichiometry: Core Concepts and Calculations

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