Question 1

Which of the following best describes why table salt (NaCl) has properties different from both sodium and chlorine?

Accepted Answer

NaCl is a compound, and compounds have emergent properties different from their constituent elements.

Question 2

Which of the following statements about isotopes is TRUE?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 3

A radioactive isotope has a half-life of 8 days. If you start with 100 grams, how much will remain after 24 days? Use the formula $$N = N_0$ 	imes (\frac{1}{2}$$)^{t/T_{1/2}$$}$$ where $$N_0 is $$the initial amount, $$t is $$time, and $$T_{1/2} is $$half-life.

Accepted Answer

12.5 grams

Question 4

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 5

Which of the following is a trace element essential for human health?

Accepted Answer

Iron (Fe)

Question 6

What is the main reason why hydrogen bonds are important in biological molecules such as DNA?

Accepted Answer

They allow for the reversible interactions necessary for biological function and structure.

Question 7

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

Accepted Answer

Covalent bonds involve the sharing of electrons, while ionic bonds involve the transfer of electrons.

Question 8

A nitrogen atom has an atomic number of 7 and a mass number of 15. How many neutrons does it have? Use the formula $$	ext{Number of neutrons} = 	ext{Mass number} - 	ext{Atomic number}.$$

Accepted Answer

8

Question 9

Which property of water allows it to be transported from the roots to the leaves in plants?

Accepted Answer

Cohesion due to hydrogen bonding

Question 10

Which of the following best explains why van der Waals interactions are important in biological systems?

Accepted Answer

They are individually weak but collectively stabilize the structures of large molecules.

Question 11

Which of the following is NOT a characteristic of living things?

Accepted Answer

Ability to form ionic compounds

Question 12

Which statement about electron shells is correct?

Accepted Answer

Electrons in shells farther from the nucleus have higher potential energy.

Question 13

Which of the following best describes the role of radioactive isotopes in medical research?

Accepted Answer

They act as tracers to follow the movement and concentration of substances in the body.

Question 14

Which of the following is true about the arrangement of elements in the periodic table?

Accepted Answer

Elements in the same group have the same number of valence electrons.

Question 15

Which of the following is a real-world application of stable isotopes in biology?

Accepted Answer

Determining the feeding relationships in an ecosystem using carbon isotope ratios

Question 16

Which of the following best explains why atoms with incomplete valence shells are chemically reactive?

Accepted Answer

They tend to share or transfer electrons to achieve stability.

Question 17

Which of the following is the correct formula for calculating the number of neutrons in an atom?

Accepted Answer

$$	ext{Number of neutrons} = 	ext{Mass number} - 	ext{Atomic number}$$

Question 18

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A compound contains two or more elements chemically combined, while a molecule can be made of the same or different elements.

Question 19

Which of the following is a consequence of the reversibility of weak chemical bonds in biological systems?

Accepted Answer

Molecules can interact temporarily and then separate, allowing dynamic biological processes.

Question 20

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity is the ability of an atom to attract electrons toward its nucleus.

Principles of Biology: Chemistry of Life and Atomic Structure

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