Q: Which of the following best describes the mole concept in chemistry?

A mole is $$6.022 \times 10$$^{23}$$ particles of a substance.

Q: How many molecules are present in 107.5 g of $$\mathrm{CH_3Cl}$$? (Molar mass of $$\mathrm{CH_3Cl} = 50.5 g/$$mol)

$$1.28 \times 10$$^{24}$$ molecules

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

$$\frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$$

Q: How many atoms of nitrogen are in 4.5 g of $$\mathrm{Cu(NO_3$)_2 \cdot 3H_2O}$$? (Molar mass = 241.6 g/mol)

$$2.25 \times 10$$^{22}$$ atoms

Q: Which of the following is the correct formula for converting grams to moles?

$$\text{Number of grams} \times \frac{1 \text{ mol}}{\text{molar mass (g)}}$$

Question 1

Which of the following best describes the mole concept in chemistry?

Accepted Answer

A mole is $$6.022 	imes 10$$^{23}$$ particles of a substance.

Question 2

How many molecules are present in 107.5 g of $$\mathrm{CH_3Cl}$$? (Molar mass of $$\mathrm{CH_3Cl} = 50.5 g/$$mol)

Accepted Answer

$$1.28 	imes 10$$^{24}$$ molecules

Question 3

A student completely reacts 12.5 g of calcium with excess oxygen to produce calcium oxide. If the actual yield is 14.5 g of calcium oxide, what is the percent yield? (Molar mass: Ca = 40.08 g/mol, CaO = 56.08 g/mol)

Accepted Answer

90.2%

Question 4

Which of the following is the correct balanced equation for the combustion of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

$$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$

Question 5

If 19.6 g of Zn reacts with 18.95 g of HCl, how many grams of $$\mathrm{H_2$}$$ are produced? (Molar masses: Zn = 65.38 g/mol, HCl = 36.5 g/mol, $$\mathrm{H_2$} = 2.02 g/$$mol)

Accepted Answer

0.520 g

Question 6

Which of the following statements about the law of conservation of mass is correct?

Accepted Answer

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

Question 7

A compound contains 68.8% C, 5.0% H, and 26.2% O by mass. What is its empirical formula?

Accepted Answer

$$\mathrm{C_7H_6O_2}$$

Question 8

Which of the following is the correct formula to calculate percent yield?

Accepted Answer

$$\frac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100\%$$

Question 9

How many atoms of nitrogen are in 4.5 g of $$\mathrm{Cu(NO_3$)_2 \cdot 3H_2O}$$? (Molar mass = 241.6 g/mol)

Accepted Answer

$$2.25 	imes 10$$^{22}$$ atoms

Question 10

A hydrocarbon has the empirical formula $$\mathrm{CH_2$}$$ and a molecular weight of 70.0 amu. What is its molecular formula?

Accepted Answer

$$\mathrm{C_5H_{10}}$$

Question 11

Which reactant is limiting if 5 mol of $$\mathrm{CH_4$}$$ and 8 mol of $$\mathrm{O_2$}$$ are mixed for the reaction $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$?

Accepted Answer

$$\mathrm{O_2$}$$

Question 12

Which of the following is NOT a type of chemical reaction?

Accepted Answer

Sublimation

Question 13

What is the molar mass of $$\mathrm{CO_2$}$$?

Accepted Answer

$$44.0 g/$$mol

Question 14

Which of the following best describes the process of mass spectrometry?

Accepted Answer

It separates ions based on their mass-to-charge ratio.

Question 15

What is the percent composition of hydrogen in ethanol ($$\mathrm{C_2H_5OH}$$)? (Molar mass = 46.07 g/mol)

Accepted Answer

13.13%

Question 16

Which of the following is the correct sequence for determining an empirical formula from percent composition?

Accepted Answer

Convert percentages to grams, convert grams to moles, divide by smallest number of moles, multiply to get whole numbers

Question 17

If you have 24 diamonds and 14 sticks, how many diamond swords (requiring 2 diamonds and 1 stick each) can you make in Minecraft, and how many sticks will be left over?

Accepted Answer

12 swords, 2 sticks left

Question 18

Which of the following is the correct formula for converting grams to moles?

Accepted Answer

$$	ext{Number of grams} 	imes \frac{1 	ext{ mol}}{	ext{molar mass (g)}}$$

Matter, Chemical Formulas, Stoichiometry, Limiting Reactant, and Percent Yield: Study Notes for General Chemistry

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