Question 1

An acid is a polar substance that dissolves in water and

Accepted Answer

An acid is a substance that donates hydrogen ions to the solution, which can combine with water molecules to form hydronium ions (H3O+). This process is reversible, and when the solution reaches equilibrium, the concentration of hydronium ions increases while the concentration of hydroxide ions (OH-) decreases. Therefore, choice D is the correct answer. Choices A and B are incorrect because an acid remains a polar substance when it dissolves in water, and it does not necessarily leave behind an OH- ion. Choice C is incorrect because an acid donates, not accepts, hydrogen ions from the solution.

Question 2

Oil and water do not mix together well because

Accepted Answer

Water is a polar molecule, meaning that it has an uneven distribution of electrons that creates a slightly negative end and a slightly positive end. Oil, on the other hand, is nonpolar and does not have these uneven charges. Polar and nonpolar substances do not mix well, so oil and water do not mix together easily.

Question 3

Which of the following pieces of evidence would best demonstrate that a bacterium found on an asteroid originated in outer space?

Accepted Answer

The presence of right-handed amino acids in the bacterium's proteins would suggest that they were not synthesized on Earth, as all life on Earth uses left-handed amino acids. This would provide evidence that the bacterium originated in outer space. The other options do not provide clear evidence of extraterrestrial origin.

Question 4

In making your morning tea,you drop a sugar cube into the hot water.You stir the mixture but no longer see the sugar cube at the bottom of your mug.In this scenario,the sugar is

Accepted Answer

The sugar cube is a solute that dissolves in the hot water, creating a sugar-water solution. The fact that it's no longer visible means it has dissolved completely, making it a solute.

Question 5

Which of the following amino acids begins the construction of all proteins in the human body?

Accepted Answer

Methionine is the amino acid that begins the construction of all proteins in the human body. It plays an important role in initiating protein synthesis and is often found at the N-terminus (beginning) of a protein chain.

Question 6

Antibodies are an important class of human proteins that function in immune defense.If scientists fragmented antibodies under laboratory conditions,what chemical building blocks would they recover?

Accepted Answer

Antibodies are made up of protein chains, which are composed of amino acids. Therefore, if antibodies were fragmented, the chemical building blocks recovered would be amino acids.

Question 7

You are given an unknown substance and asked to determine whether it is polar or nonpolar.The easiest way to do this would be to

Accepted Answer

The best way to determine whether a substance is polar or nonpolar is to determine whether it dissolves in water. Polar substances will dissolve in water, whereas nonpolar substances will not. This is because water is a polar molecule and will attract other polar molecules, but not nonpolar molecules. Therefore, if the unknown substance dissolves in water, it is likely polar, whereas if it does not dissolve, it is likely nonpolar.

Question 8

Of the following values,which indicates the most basic pH?

Accepted Answer

The pH scale ranges from 0 to 14, where a pH of 7 is neutral, anything below 7 is acidic, and anything above 7 is basic. Therefore, a pH of 10 is more basic than a pH of 8 or 5, making choice D the correct answer.

Question 9

When sodium chloride (Na⁺Cl⁻)is dissolved in water,the sodium ion

Accepted Answer

The sodium ion (Na⁺) is positively charged and is therefore attracted to the negatively charged oxygen atoms of water molecules. This attraction between the ions and water molecules is known as hydration. The chloride ion (Cl⁻) is negatively charged and is attracted to the positively charged hydrogen atoms of water molecules.

Question 10

The pH scale measures

Accepted Answer

The pH scale measures the concentration of hydrogen ions (H+) in a solution. The pH scale ranges from 0 to 14, with a pH of 7 considered neutral, pH values less than 7 indicating acidity, and pH values greater than 7 indicating alkalinity or basicity.

Question 11

How many different amino acids are used to build proteins?

Accepted Answer

There are 20 different amino acids used to build proteins.

Question 12

Neighboring water molecules are held together with hydrogen bonds because

Accepted Answer

Hydrogen bonds are formed between neighboring water molecules because the partially negatively charged oxygen atom of one water molecule is attracted to the partially positively charged hydrogen atom of another water molecule. This attraction results in a weak electrostatic bond known as a hydrogen bond.

Question 13

In living systems,a critical component of many reactions is

Accepted Answer

Water is an essential component in many reactions in living systems, including photosynthesis, cellular respiration, and many metabolic pathways. It serves as a solvent, facilitates chemical reactions, and helps regulate body temperature. While carbon dioxide, calcium, and hydrogen sulfide can also play important roles in living systems, water is the most critical component in many reactions.

Question 14

When ammonia (NH₃)is dissolved in a solution,it accepts hydrogen ions from its surroundings.Ammonia is therefore

Accepted Answer

Ammonia accepts hydrogen ions and therefore acts as a proton acceptor or a base.

Question 15

A solution with a pH of 3 is

Accepted Answer

A solution with a pH of 3 is considered acidic. The pH scale ranges from 0 to 14, with 7 being neutral, below 7 being acidic, and above 7 being basic. Therefore, a pH of 3 falls firmly on the acidic side of the scale.

Question 16

A carwash attendant offers to treat your windshield with a protective agent.This substance coats the glass,causing beads of water to easily roll off during a rain shower.Which of the following must be correct about the protective agent?

Accepted Answer

The protective agent causes water to bead and easily roll off, indicating that it is hydrophobic (repels water). The other options do not necessarily apply to a substance that provides this type of protection.

Question 17

After adding a small amount of Solution A to Solution B,the pH of Solution B declines from 8 to 3.Solution A must contain

Accepted Answer

The decrease in pH from 8 to 3 indicates that Solution A is an acid, which would cause the pH of Solution B to decrease when added to it. Therefore, the correct answer is D) an acid.

Question 18

Which of the following solutions has the highest concentration of free H⁺ ions?

Accepted Answer

The pH scale is a measure of the concentration of H⁺ ions in a solution, with lower pH values corresponding to higher H⁺ concentrations. A pH of 1 has the highest concentration of free H⁺ ions, making choice A the correct answer.

Question 19

In making your morning tea,you drop a sugar cube into some hot water.You stir the mixture but no longer see the sugar cube at the bottom of your mug.Based on your observation of sugar dissolving in hot water,you properly conclude that the sugar is

Accepted Answer

The sugar cube dissolved in hot water, which indicates that it is hydrophilic, meaning it has an affinity for water and can dissolve in it. Hydrophobic substances repel water and would not dissolve in it. Nonpolar and inert do not accurately describe the sugar's behavior in this situation.

Question 20

Which of the following explains why ice floats on water?

Accepted Answer

The distance between water molecules in ice is greater than in liquid water, making ice less dense than water, which is why it floats.

Quiz 2: Chemistry of Life