Question 1

Which of the following best describes the difference between a scientific law and a scientific theory?

Accepted Answer

A scientific law describes a consistent relationship observed in nature, often expressed mathematically, while a scientific theory explains the underlying reasons for those relationships.

Question 2

A student measures the mass of a sample three times and records the values: 2.51 g, 2.50 g, and 2.52 g. The true mass is 2.80 g. Which statement best describes the student's measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following is the correct way to express 0.0004560 in scientific notation, including the correct number of significant figures?

Accepted Answer

$$4.560 	imes 10$$^{-4}$$

Question 4

A sample of a metal has a mass of 13.5 g and a volume of 1.50 cm$$^3. $$What is its density?

Accepted Answer

$$9.00\ \mathrm{g/cm^3$}$$

Question 5

Which of the following best describes an endothermic process?

Accepted Answer

A process in which the system absorbs heat from the surroundings, such as melting ice.

Question 6

A chemical reaction absorbs 150 J of heat and the temperature of 10.0 g of water increases by $$3.6\ ^\circ\mathrm{C}. $$What is the specific heat capacity $$c of $$water based on this experiment? (Use $$q = mc\Delta T)$$

Accepted Answer

$$4.17\ \mathrm{J/g\ ^\circ C}$$

Question 7

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 8

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many protons, neutrons, and electrons does it have?

Accepted Answer

17 protons, 18 neutrons, 17 electrons

Question 9

Which of the following compounds is an example of a molecular compound?

Accepted Answer

CO$$_2$$

Question 10

Calculate the mass percent of oxygen in H$$_2O. ($$Molar mass: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$88.8\%$$

Question 11

A sample contains 0.250 mol of NaCl. How many formula units of NaCl are present? (Avogadro's number $$= 6.022 	imes 10$$^{23}$$ mol$$^{-1}$$)

Accepted Answer

$$1.51 	imes 10$$^{23}$$

Question 12

Which of the following is a balanced chemical 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 13

Which of the following best explains why ionic compounds generally have higher melting points than molecular compounds?

Accepted Answer

Ionic compounds are held together by strong electrostatic forces between ions, while molecular compounds are held together by weaker intermolecular forces.

Question 14

A 2.00 L container holds 0.0800 mol of an ideal gas at 300 K. What is the pressure in the container? (Use $$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$0.984\ \mathrm{atm}$$

Question 15

Which of the following statements about hydrogen bonding is correct?

Accepted Answer

Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms such as N, O, or F, resulting in unusually strong dipole-dipole attractions.

Question 16

A solution is prepared by dissolving 10.0 g of NaCl in enough water to make 500.0 mL of solution. What is the molarity of the solution? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$0.342\ \mathrm{M}$$

Question 17

Which of the following changes will shift the equilibrium of the reaction $$\mathrm{N_2$}(g) + 3\ \mathrm{H_2$}(g) \rightleftharpoons 2\ \mathrm{NH_3$}(g) to $$the right (toward products)?

Accepted Answer

Increasing the pressure by decreasing the volume of the container.

Question 18

Which of the following is a strong electrolyte when dissolved in water?

Accepted Answer

NaCl

Question 19

A radioactive isotope has a half-life of 3.0 hours. If you start with 80.0 g, how much remains after 9.0 hours?

Accepted Answer

$$10.0\ \mathrm{g}$$

Introduction to Chemistry: Curriculum Map and Key Concepts

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