Q: A student is given a sample of an unknown metal and asked to determine its identity. She measures its mass as 19.6 g and its volume as 2.5 mL. Which equation should she use to calculate the density, and what is the density of the metal?

Use $$\text{Density} = \frac{\text{mass}}{\text{volume}}$$; density is $$7.84\ \text{g/mL}.$$

Q: A balloon filled with helium gas has a volume of 2.0 L at a pressure of 1.0 atm. If the pressure is increased to 2.0 atm at constant temperature, what will the new volume be? (Assume ideal gas behavior.)

Use $$P_1V_1 = P_2V_2$$; new volume is $$1.0\ \text{L}.$$

Q: A sample contains 0.50 moles of NaCl. What is the mass of this sample? (Molar mass of NaCl = 58.44 g/mol)

Use $$\text{mass} = \text{moles} \times \text{molar mass}$$; mass is $$29.22\ \text{g}.$$

Question 1

Which of the following best describes the scientific method as it is applied in chemistry?

Accepted Answer

A systematic approach involving observation, hypothesis formation, experimentation, and analysis to understand natural phenomena.

Question 2

A student is given a sample of an unknown metal and asked to determine its identity. She measures its mass as 19.6 g and its volume as 2.5 mL. Which equation should she use to calculate the density, and what is the density of the metal?

Accepted Answer

Use $$	ext{Density} = \frac{	ext{mass}}{	ext{volume}}$$; density is $$7.84\ 	ext{g/mL}.$$

Question 3

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 4

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

Water has a bent molecular geometry and an uneven distribution of electron density due to the difference in electronegativity between hydrogen and oxygen.

Question 5

A balloon filled with helium gas has a volume of 2.0 L at a pressure of 1.0 atm. If the pressure is increased to 2.0 atm at constant temperature, what will the new volume be? (Assume ideal gas behavior.)

Accepted Answer

Use $$P_1V_1 = P_2V_2$$; new volume is $$1.0\ 	ext{L}.$$

Question 6

Which of the following is an example of a chemical change?

Accepted Answer

A piece of iron rusts when left outside in the rain.

Question 7

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons from one atom to another, while covalent bonds involve the sharing of electrons between atoms.

Question 8

A sample contains 0.50 moles of NaCl. What is the mass of this sample? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

Use $$	ext{mass} = 	ext{moles} 	imes 	ext{molar mass}$$; mass is $$29.22\ 	ext{g}.$$

Question 9

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have completely filled valence electron shells, making them stable.

Question 10

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

Accepted Answer

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

Question 11

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

Use $$	ext{Molarity} = \frac{	ext{moles}}{	ext{liters}}$$; molarity is $$0.342\ 	ext{M}.$$

Question 12

Which of the following best describes the process of radioactive decay?

Accepted Answer

The spontaneous transformation of an unstable atomic nucleus into a more stable one, often accompanied by the emission of particles or energy.

Question 13

Which of the following statements about acids and bases is correct according to the Brønsted-Lowry definition?

Accepted Answer

An acid is a proton ($$\mathrm{H^+}) $$donor and a base is a proton ($$\mathrm{H^+}) $$acceptor.

Question 14

Which of the following best explains why salt (NaCl) dissolves in water?

Accepted Answer

The polar water molecules surround and stabilize the Na$$^+$$ and Cl$$^-$$ ions, allowing them to separate and disperse in solution.

Question 15

A chemical reaction is at equilibrium when:

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 16

Which of the following best describes the trend in atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right across a period.

Question 17

A patient receives 500 mg of a medication. If the molar mass of the medication is 250 g/mol, how many moles of the medication did the patient receive?

Accepted Answer

Use $$	ext{moles} = \frac{	ext{mass (g)}}{	ext{molar mass (g/mol)}}$$; moles = $$0.002\ 	ext{mol}.$$

Question 18

Which of the following is a correct application of the law of conservation of mass in a chemical reaction?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 19

Which of the following best describes the role of catalysts in chemical reactions?

Accepted Answer

Catalysts lower the activation energy, increasing the rate of reaction without being consumed.

CHEM 101: Introduction to Chemistry – Syllabus and Course Structure Study Guide

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