Question 1

Which of the following observed properties is most reliable in classifying a substance as a metal?

Accepted Answer

Metals are known for their ability to conduct heat and electricity efficiently, making "good conductor of heat" a reliable property for classifying a substance as a metal.

Question 2

Which of the following statements describes an exothermic reaction but not an endothermic reaction?

Accepted Answer

Exothermic reactions release energy, often in the form of heat, as products are formed, which is not characteristic of endothermic reactions. Endothermic reactions absorb energy from the surroundings.

Question 3

Which of the following statements explains why oxygen is classified asa pure substance and air is classifiedas a mixture?

Accepted Answer

Oxygen is considered a pure substance because it consists of only one type of molecule, O2, whereas air is a mixture because it contains a variety of gases such as nitrogen, oxygen, carbon dioxide, and others in varying proportions.

Question 4

The pH of milk is 6.4. Based on this information, which of the following statements best describes milk?

Accepted Answer

Milk with a pH of 6.4 is slightly acidic since it is below 7 but close to neutral, indicating it is not strongly acidic.

Question 5

A student made a homogeneous mixture of water and salt. Which of the following statements applies to this homogeneous mixture?

Accepted Answer

A homogeneous mixture where the components are evenly distributed on a molecular level, such as salt dissolved in water, is known as a solution.

Question 6

Which of the following statements best explains why elements in the same family of the periodic table have similar bonding properties?

Accepted Answer

Elements in the same family (or group) of the periodic table have similar valence electron configurations, which determines their bonding properties. The number of valence electrons influences how elements interact with other elements, leading to similarities in chemical behavior within a group.

Question 7

Which of the following statements describes all exothermic reactions?

Accepted Answer

Exothermic reactions release energy, meaning the energy of the reactants is higher than the energy of the products. This energy difference is released into the surroundings, often as heat.

Question 8

Which of the following statements best explains why potassium (K) reacts easily with bromine (Br)?

Accepted Answer

Potassium (K) has one electron in its outermost shell (making it eager to lose that electron to achieve a stable electronic configuration), while bromine (Br) has seven electrons in its outermost shell and needs one more to complete its octet (making it eager to gain an electron). This complementary need for electrons facilitates the reaction between them.

Question 9

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 10

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. This is because buffers in the blood can neutralize excess acids or bases, maintaining the pH within a narrow range essential for proper physiological functions.

Question 11

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 atoms split into smaller parts. This principle is harnessed in nuclear power plants to generate electricity, demonstrating the large energy release characteristic of fission processes.

Question 12

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 means the substance is transitioning from a solid state (below its melting point of -92°C) to a liquid state. In the liquid state, molecules move more freely compared to their movement in the solid state, where they are held in a fixed position within a crystal structure. The other options (B and C) do not typically occur with a simple temperature change in this context, and D describes the opposite process of melting.

Question 13

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. A smaller volume of solvent with the same amount of solute results in a higher concentration. Therefore, 0 mol solute in 200 mL solvent has the highest concentration among the options provided.

Question 14

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 15

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 16

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 its positive charge are concentrated in a small area at the center of the atom, which he called the nucleus. This experiment showed that the atom is mostly empty space, with electrons orbiting a dense nucleus.

Question 17

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 tend to share electrons equally, resulting in a nonpolar covalent bond.

Question 18

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

Accepted Answer

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

Question 19

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

Accepted Answer

Mixtures can have varying compositions because they consist of two or more substances mixed together in varying proportions. Pure substances, on the other hand, have a fixed composition with unique properties throughout.

Question 20

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

Accepted Answer

The unique brightline spectrum emitted by each element when it falls from an excited state to a ground state directly supports Bohr's idea that electrons occupy specific energy levels. When electrons transition between these levels, they emit or absorb photons of specific energies, resulting in the unique spectral lines for each element.

Quiz 2: Chemistry