Question 1

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

Accepted Answer

A molecule consists of two or more atoms of the same element, while a compound consists of atoms of different elements.

Question 2

Which element makes up the largest percentage of human body weight, including water?

Accepted Answer

Oxygen

Question 3

A sodium atom ($$\mathrm{Na}) $$reacts with a chlorine atom ($$\mathrm{Cl}) to $$form sodium chloride ($$\mathrm{NaCl}). $$What type of bond is formed between sodium and chlorine?

Accepted Answer

Ionic bond

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 5

Which property of water allows it to climb up the stem of a plant against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 6

If a solution has a $$[\mathrm{H}^+]$$ concentration of $$1 	imes 10$$^{-4}$$ M, what is its pH?

Accepted Answer

$$4$$

Question 7

Which of the following best explains why water is considered a universal solvent?

Accepted Answer

Water molecules form hydrogen bonds with both positive and negative ions, allowing many substances to dissolve.

Question 8

Which of the following is a trace element in the human body, making up less than 0.01% of body weight?

Accepted Answer

Iron

Question 9

A radioactive isotope of carbon, $$^{14}\mathrm{C}$$, is used in radiometric dating. What makes $$^{14}\mathrm{C}$$ radioactive compared to $$^{12}\mathrm{C}$$?

Accepted Answer

$$^{14}\mathrm{C}$$ has an unstable nucleus due to extra neutrons.

Question 10

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

Accepted Answer

A buffer is a substance that resists changes in pH by absorbing or releasing $$\mathrm{H}^+ or$$ $$\mathrm{OH}^-$$ ions.

Question 11

Which of the following is true about the atomic number of an element?

Accepted Answer

It is equal to the number of protons in the atom.

Question 12

Which type of chemical bond is responsible for the structure of a water molecule ($$\mathrm{H}_2\mathrm{O}$$)?

Accepted Answer

Covalent bond

Question 13

A solution has a pH of 3. Which of the following statements is correct?

Accepted Answer

The solution is acidic and has a higher concentration of $$\mathrm{H}^+$$ than $$\mathrm{OH}^-.$$

Question 14

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

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds hold water molecules further apart in the solid state.

Question 15

Which of the following is an example of a polar covalent bond?

Accepted Answer

The bond between hydrogen and oxygen in a water molecule

Question 16

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons and has a positive charge.

Question 17

Which of the following is a real-world example of a reversible chemical reaction reaching equilibrium?

Accepted Answer

The dissociation of water: $$2\mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{H}_3\mathrm{O}^+ + \mathrm{OH}^-$$

Question 18

Which of the following best describes the reductionist approach in biology?

Accepted Answer

Breaking down biological systems into their chemical and physical components to understand their function.

Question 19

Which of the following statements about electron shells is correct?

Accepted Answer

The outermost electron shell is called the valence shell and determines chemical reactivity.

The Chemical Basis of Life: Atoms, Elements, and Chemical Bonds

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