Q: A sample of nitrogen gas occupies 16.0 L at 1.37 atm and 315 K. How many moles of nitrogen gas are present? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

$$n = \frac{PV}{RT} = \frac{1.37 \times 16.0}{0.0821 \times 315} = 0.845$$

Q: A solution is made from 12.6 g of NaCl and 100 g of water. What is the mass percent of NaCl in the solution?

$$\frac{12.6}{12.6 + 100} \times 100\% = 11.2\%$$

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

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

Question 1

Which of the following best describes the difference between a compound and a homogeneous mixture?

Accepted Answer

A compound is composed of two or more elements in fixed, definite proportions, while a homogeneous mixture contains substances that are uniformly mixed but not chemically bonded.

Question 2

A student measures the mass of a rock as 21.622 g. The initial water level in a graduated cylinder is 30.0 mL, and after the rock is added, the water level rises to 37.3 mL. What is the density of the rock, and how many significant figures should the answer have?

Accepted Answer

Density = $$\frac{21.622\ \mathrm{g}}{7.3\ \mathrm{mL}} = 2.96\ \mathrm{g/mL}$$, 3 significant figures

Question 3

Which of the following is a chemical property?

Accepted Answer

Flammability

Question 4

A solution is made by dissolving 15.0 g of KNO$$_3 in 150.0 mL of $$solution. What is the molarity of the solution? (Molar mass of KNO$$_3 = 101.1 g/$$mol)

Accepted Answer

$$M = \frac{15.0\ \mathrm{g}}{101.1\ \mathrm{g/mol}} \div 0.150\ \mathrm{L} = 0.99\ \mathrm{M}$$

Question 5

Which of the following molecules is nonpolar?

Accepted Answer

CO$$_2$$

Question 6

A gold crown has a mass of 883.39 g. If the density of gold is 19.3 g/mL, what is the volume of the crown?

Accepted Answer

$$V = \frac{883.39\ \mathrm{g}}{19.3\ \mathrm{g/mL}} = 45.8\ \mathrm{mL}$$

Question 7

Which of the following best describes the role of a buffer in a solution?

Accepted Answer

A buffer resists changes in pH when small amounts of acid or base are added.

Question 8

Which of the following is the correct electron configuration for the N$$^{3-}$$ ion?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 9

A sample of nitrogen gas occupies 16.0 L at 1.37 atm and 315 K. How many moles of nitrogen gas are present? ($$R = 0.0821\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$n = \frac{PV}{RT} = \frac{1.37 	imes 16.0}{0.0821 	imes 315} = 0.845$$

Question 10

Which of the following statements about acids is FALSE?

Accepted Answer

Acids have a slippery feel.

Question 11

A solution is made from 12.6 g of NaCl and 100 g of water. What is the mass percent of NaCl in the solution?

Accepted Answer

$$\frac{12.6}{12.6 + 100} 	imes 100\% = 11.2\%$$

Question 12

Which of the following is the correct balanced equation for the combustion of glucose ($$\mathrm{C_6H_{12}O_6$}$$)?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 6\mathrm{O_2$} \rightarrow 6\mathrm{CO_2$} + 6\mathrm{H_2O}$$

Question 13

Which of the following substances is most likely to be soluble in water?

Accepted Answer

CH$$_3OH$$

Question 14

A radioactive isotope has a half-life of 8 days. If you start with 88 mg, how much remains after 24 days?

Accepted Answer

11 mg

Question 15

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

Accepted Answer

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

Question 16

Which of the following best describes the process of drawing a Lewis dot diagram for a polyatomic ion?

Accepted Answer

Count the total number of valence electrons, add electrons for negative charge, subtract for positive charge, arrange atoms, connect with bonds, and distribute remaining electrons to satisfy the octet rule.

Question 17

Which of the following is a correct application of the multiplication/division rule for significant figures?

Accepted Answer

$$3.69 	imes 2.3059 = 8.51 ($$rounded to three significant figures)

Question 18

Which of the following best explains why real gases deviate from ideal gas behavior at low temperatures and high pressures?

Accepted Answer

At low temperatures and high pressures, intermolecular attractions become significant and the volume of gas particles is no longer negligible.

Introductory Chemistry: Comprehensive Final Exam Review Notes

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