Question 1

Which of the following statements best explains why atoms bond?

Accepted Answer

Atoms bond to become more chemically stable. This is because by sharing or transferring electrons through bonds, atoms achieve a full outer electron shell, resembling the electron configuration of noble gases, which is the most stable arrangement.

Question 2

When a sample of potassium chloride dissolves in water, it separates into potassium ions and chloride ions. Which of the following best accounts for the positive charge of the potassium ions?

Accepted Answer

Potassium ions have a positive charge because they have fewer electrons than protons. When potassium loses an electron, it has more protons than electrons, resulting in a net positive charge.

Question 3

Which of the following characteristics allows blood to resist changes in pH?

Accepted Answer

Blood's buffering capacity allows it to resist changes in pH by neutralizing acids and bases, maintaining a stable pH essential for proper physiological function.

Question 4

Which of the following statements applies to a nuclear fission reaction?

Accepted Answer

Nuclear fission reactions release significant amounts of energy as the nuclei of certain heavy elements, such as uranium or plutonium, split into smaller fragments. This process is the basis for nuclear power generation and atomic bombs, highlighting its capability to release large energy quantities.

Question 5

Gold-198 has a half-life of approximately 3 days. If a 100 g sample of gold-198 decays for 9 days, approximately how much gold-198 remains in the sample?

Accepted Answer

After 9 days, which is three half-lives of gold-198 (3 days per half-life), the amount remaining would be $100g \times (\frac{1}{2})^3 = 100g \times \frac{1}{8} = 12.5g$, which rounds to approximately 13g.

Question 6

Formaldehyde in solution is used as a preservative. It has a melting point of -92°C. When the temperature of a sample of formaldehyde rises from -93°C to -91°C, which of the following occurs?

Accepted Answer

When the temperature of formaldehyde rises from -93°C to -91°C, it transitions from a solid to a liquid state (since its melting point is -92°C). In this liquid state, the molecules move more freely compared to their movement in the solid state.

Question 7

Which of the following solutions has the highest concentration of solute?

Accepted Answer

The concentration of a solution is determined by the ratio of solute to solvent. The highest concentration means the greatest amount of solute per unit volume of solvent. For A) 1.0 mol in 200 mL equals 5 mol/L, which is higher than the concentrations calculated for the other options (B) 4 mol/L, (C) 3 mol/L, and (D) 2.67 mol/L.

Question 8

A hiker carries drinking water in a cloth-covered, metal container called a canteen. During the summer, the hiker wets the cloth covering so that the water in the canteen stays cool. Which of the following statements explains why a wet covering keeps the water cool?

Accepted Answer

Evaporation of water from the covering absorbs heat from the surrounding environment, including the canteen, to change the water from liquid to vapor. This process effectively removes heat from the canteen, keeping the water inside cooler.

Question 9

Which of the following statements explains what happens to the gas inside a balloon as the external pressure on the balloon decreases and the temperature stays constant?

Accepted Answer

When the external pressure on a balloon decreases while the temperature remains constant, the gas inside the balloon expands due to reduced external pressure, leading to an increase in volume according to Boyle's Law.

Question 10

Which of the following statements best explains why ice floats on water?

Accepted Answer

Hydrogen bonding in water leads to a unique structure when it freezes, causing ice to expand and become less dense than liquid water. This lower density is why ice floats on water.

Question 11

Which of the following did scientists learn about the atom from Rutherford's gold foil experiment?

Accepted Answer

Rutherford's gold foil experiment led to the discovery that an atom's mass and positive charge are concentrated in a small central nucleus, disproving the earlier plum pudding model which suggested that positive charge was spread evenly throughout the atom.

Question 12

Two elements in a molecule have the same electronegativity values. Which of the following most likely holds the elements together and why?

Accepted Answer

When two elements in a molecule have the same electronegativity values, they share electrons equally, leading to a nonpolar covalent bond. This is because there is no electronegativity difference to create an uneven distribution of electron density.

Question 13

Which of the following statements best explains why water vapor condenses as temperature decreases?

Accepted Answer

As the temperature decreases, the kinetic energy of water vapor molecules decreases, allowing the intermolecular attractive forces (such as hydrogen bonding) to become more effective in pulling the molecules closer together, leading to condensation.

Question 14

Which of the following elements is a member of the halogen family and is located in period 3?

Accepted Answer

Chlorine (Cl) is the correct answer because it is a halogen and is located in period 3 of the periodic table. Halogens are found in Group 17, and chlorine is the only element listed that meets both criteria.

Question 15

Which of the following statements describes a difference between a mixture and a pure substance?

Accepted Answer

The composition of a mixture can vary because it is made up of two or more different substances that are physically combined, not chemically. In contrast, a pure substance has a fixed composition because it consists of a single type of element or compound.

Question 16

Which of the following pieces of evidence best supports Bohr's idea that electrons occupy specific energy levels within an atom?

Accepted Answer

Bohr's model of the atom proposes that electrons orbit the nucleus in specific energy levels or shells. The unique brightline spectrum emitted by each element when it falls from an excited state to a ground state directly supports this idea, as these spectral lines are the result of electrons moving between these defined energy levels and releasing energy in the form of light at specific wavelengths.

Question 17

The air inside a beach ball is at a temperature of 25°C and a pressure of 1.0 atm. If the ball contains 0.85 mol of air, what is its volume?

Accepted Answer

Using the ideal gas law, $PV = nRT$, where $P = 1.0 \, \text{atm}$, $n = 0.85 \, \text{mol}$, $R = 0.0821 \, \text{L atm mol}^{-1} \text{K}^{-1}$, and $T = 25°C = 298K$, the volume $V$ can be calculated as $V = \frac{nRT}{P} = \frac{0.85 \times 0.0821 \times 298}{1.0} \approx 21 \, \text{L}$.

Question 18

Which of the following correctly pairs a phase of matter with its description?

Accepted Answer

In the gas phase, particles have higher amounts of energy compared to when they are in the liquid phase, allowing them to move more freely and occupy a greater volume.

Question 19

Which of the following sections of the periodic table contains only metals?

Accepted Answer

Group 2 of the periodic table consists entirely of metals, known as the alkaline earth metals, including beryllium, magnesium, calcium, strontium, barium, and radium.

Question 20

An insect known as a water strider can walk across the surface of a pond. Which of the following is directly responsible for this insect being able to walk on the surface without sinking?

Accepted Answer

Hydrogen bonding is directly responsible for the high surface tension of water, which allows water striders to walk on the surface without sinking. This type of bonding occurs between water molecules, creating a "skin" on the water's surface that can support the weight of small organisms like water striders.

Quiz 2: Chemistry