Question 1

Which of the following best describes a trace element?

Accepted Answer

An element required by an organism in only minute quantities

Question 2

A neutral atom of sodium (Na) has an atomic number of 11 and an atomic mass of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which statement correctly compares ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons, while covalent bonds involve the sharing of electrons.

Question 4

Which of the following molecules is most likely to form hydrogen bonds with water?

Accepted Answer

Ammonia ($$NH_3)$$

Question 5

If the pH of a solution changes from 6 to 3, how much more acidic has the solution become?

Accepted Answer

$$10^{(6-3)}$$ = $$10^3 = 1000$ times more acidic

Question 6

Which property of water explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds stabilize and keep the molecules farther apart in ice than in liquid water.

Question 7

A solution has a pH of 8. Which of the following best describes this solution?

Accepted Answer

It is basic (alkaline).

Question 8

Which of the following best describes the role of a buffer in biological systems?

Accepted Answer

It minimizes changes in pH by accepting or donating $$H^+$$ ions.

Question 9

How many electrons can occupy the first and second electron shells of an atom, respectively?

Accepted Answer

2 in the first shell, 8 in the second shell

Question 10

A chlorine atom has 7 electrons in its valence shell. How many covalent bonds can it form?

Accepted Answer

1

Question 11

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

Accepted Answer

The polar water molecules surround and separate the positive $$Na^+$$ and negative $$Cl^-$$ ions.

Question 12

Which of the following is NOT a property of water resulting from hydrogen bonding?

Accepted Answer

Water's ability to dissolve nonpolar molecules

Question 13

A radioactive isotope differs from a stable isotope of the same element in that it:

Accepted Answer

Has an unstable nucleus that decays over time, emitting radiation

Question 14

Which of the following best describes an ion?

Accepted Answer

An atom or molecule with a net electrical charge due to the loss or gain of electrons

Question 15

If you add a strong acid to a buffered solution, what will happen to the pH compared to adding the same acid to pure water?

Accepted Answer

The pH will decrease less in the buffered solution than in pure water.

Question 16

Which of the following best describes the difference between heat and temperature?

Accepted Answer

Heat is the total energy of molecular motion, while temperature is the average kinetic energy of molecules.

Question 17

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

Accepted Answer

Hydrogen gas and oxygen gas combine to form water: $$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 18

Which of the following best describes a solution?

Accepted Answer

A homogeneous mixture of a solute dissolved in a solvent

Question 19

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons are found in the outermost electron shell and determine an atom's chemical properties.

Question 20

A solution has a pH of 7. Which of the following statements is true?

Accepted Answer

The solution is neutral, with equal concentrations of $$H^+$$ and $$OH^-$$ ions.

Essential Chemistry for Biology – Guided Study Support

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