Q: A sample of gas occupies 2.00 L at 1.00 atm. If the pressure is increased to 4.00 atm at constant temperature, what will be the new volume of the gas? (Assume ideal gas behavior.)

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 \times 2.00}{4.00} = 0.50$$ L

Q: A chemist needs to prepare 250.0 mL of a 0.100 M NaCl solution. How many grams of NaCl are required? ($$M_{NaCl} = 58.44 g/$$mol)

$$0.100 \times 0.250 = 0.025$$ mol; $$0.025 \times 58.44 = 1.46 g$$

Q: A student is asked to convert 25.0 cm to meters using dimensional analysis. Which setup is correct?

$$25.0 \text{ cm} \times \frac{1 \text{ m}}{100 \text{ cm}} = 0.250 \text{ m}$$

Question 1

Which of the following best describes the difference between a physical change and a chemical change? Choose the most accurate statement.

Accepted Answer

A chemical change results in the formation of new substances with different chemical properties, while a physical change does not alter the chemical identity of the substance.

Question 2

A student measures the mass of a metal sample as 12.45 g and its volume as 2.50 mL. What is the density of the metal, and which significant figures rule applies to the answer?

Accepted Answer

Density = $$\frac{12.45}{2.50} = 4.98 g/mL$$; answer should have 3 significant figures because volume has 3.

Question 3

Which of the following is the correct scientific notation for the number 0.000345?

Accepted Answer

$$3.45 	imes 10$$^{-4}$$

Question 4

A sample of gas occupies 2.00 L at 1.00 atm. If the pressure is increased to 4.00 atm at constant temperature, what will be the new volume of the gas? (Assume ideal gas behavior.)

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.00 	imes 2.00}{4.00} = 0.50$$ L

Question 5

Which statement best explains why water boils at a lower temperature at higher altitudes?

Accepted Answer

The atmospheric pressure is lower, so the vapor pressure required for boiling is reached at a lower temperature.

Question 6

Which of the following best describes the particulate theory of matter?

Accepted Answer

Matter is composed of tiny particles called atoms or molecules, which are in constant motion.

Question 7

A chemist needs to prepare 250.0 mL of a 0.100 M NaCl solution. How many grams of NaCl are required? ($$M_{NaCl} = 58.44 g/$$mol)

Accepted Answer

$$0.100 	imes 0.250 = 0.025$$ mol; $$0.025 	imes 58.44 = 1.46 g$$

Question 8

Which of the following is NOT a correct statement about the ideal gas law?

Accepted Answer

The ideal gas law accurately describes the behavior of all gases under all conditions.

Question 9

A mixture contains sand, salt, and water. Which separation technique would best isolate the salt from the mixture?

Accepted Answer

Filtration followed by evaporation of the water.

Question 10

Which of the following is the correct electron configuration for a neutral oxygen atom?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^4$$

Question 11

A student is asked to convert 25.0 cm to meters using dimensional analysis. Which setup is correct?

Accepted Answer

$$25.0 	ext{ cm} 	imes \frac{1 	ext{ m}}{100 	ext{ cm}} = 0.250 	ext{ m}$$

Question 12

Which of the following statements about intermolecular forces is correct?

Accepted Answer

Hydrogen bonding is generally stronger than London dispersion forces.

Question 13

A solution is prepared by dissolving 5.00 g of KCl in enough water to make 200.0 mL of solution. What is the molarity of the solution? ($$M_{KCl} = 74.55 g/$$mol)

Accepted Answer

$$\frac{5.00}{74.55} = 0.0671$$ mol; $$M = \frac{0.0671}{0.200} = 0.336 M$$

Question 14

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

Strong electrostatic forces between oppositely charged ions require a large amount of energy to break.

Question 15

A chemical reaction has a percent yield of 80%. If the theoretical yield is 25.0 g, what is the actual yield?

Accepted Answer

$$	ext{Actual yield} = \frac{80}{100} 	imes 25.0 = 20.0 g$$

Question 16

Which of the following is the correct balanced equation for the reaction of sodium with water?

Accepted Answer

$$2Na + 2H_2O \rightarrow 2NaOH + H_2$

Question 17

Which statement best describes the difference between empirical and molecular formulas?

Accepted Answer

The empirical formula shows the simplest whole-number ratio of atoms, while the molecular formula shows the actual number of atoms in a molecule.

Question 18

A student mixes 50.0 mL of 0.200 M HCl with 50.0 mL of 0.200 M NaOH. What is the final concentration of NaCl formed?

Accepted Answer

Moles HCl = $$0.050 	imes 0.200 = 0.010$$ mol; Moles NaOH = $$0.050 	imes 0.200 = 0.010$$ mol; Total volume = $$0.100 L$$; $$M_{NaCl} = \frac{0.010}{0.100} = 0.100 M$$

Question 19

Which of the following best describes the VSEPR theory?

Accepted Answer

VSEPR theory predicts the shapes of molecules based on the repulsion between electron pairs around a central atom.

Introductory Chemistry 22: Course Syllabus and Study Guide

Guida di studio - Domande di pratica

Study guide - Flashcard