$$pH = -\log(1 \times 10$$^{-5}$$) = 5$$

Question 1

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

Accepted Answer

Covalent bonds involve the sharing of electrons between atoms, while ionic bonds involve the transfer of electrons from one atom to another.

Question 2

Given the following electronegativity values: O = 3.5, H = 2.1, which type of bond is formed between oxygen and hydrogen in a water molecule?

Accepted Answer

A polar covalent bond, because electrons are shared unequally.

Question 3

Which property of water allows insects to walk on its surface?

Accepted Answer

High surface tension due to cohesion between water molecules.

Question 4

If a solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$ \ \mathrm{M}$$, what is its pH?

Accepted Answer

$$pH = -\log(1 	imes 10$$^{-5}$$) = 5$$

Question 5

Which of the following functional groups acts as a base and can accept a proton?

Accepted Answer

Amino group ($$-NH_2$)

Question 6

What happens during a condensation (dehydration synthesis) reaction?

Accepted Answer

Two monomers are joined together and a molecule of water is released.

Question 7

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

Accepted Answer

Hydrogen bonds in ice keep water molecules farther apart, making ice less dense than liquid water.

Question 8

A molecule that donates a proton ($$H^+) $$during a chemical reaction is classified as:

Accepted Answer

An acid

Question 9

Which of the following molecules is most likely to dissolve in water?

Accepted Answer

Glucose ($$C_6H_{12}O_6$), because it contains many polar hydroxyl groups.

Question 10

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by accepting or donating $$H^+$$ ions.

Question 11

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds form between a hydrogen atom with a partial positive charge and an electronegative atom (like O or N) with a partial negative charge.

Question 12

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

Accepted Answer

The partial charges on water molecules surround and stabilize the Na$$^+$$ and Cl$$^-$$ ions.

Question 13

Which of the following is true about the relationship between bond polarity and potential energy?

Accepted Answer

Nonpolar covalent bonds have higher potential energy than polar covalent bonds.

Question 14

Which of the following functional groups is most likely to act as an acid in solution?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 15

A hydrolysis reaction is best described as:

Accepted Answer

Breaking a polymer into monomers by adding water.

Question 16

Which of the following best describes the emergent property of water that allows lakes to remain liquid under a layer of ice in winter?

Accepted Answer

Ice is less dense than liquid water, so it floats and insulates the water below.

Question 17

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

Accepted Answer

Water’s polarity allows it to dissolve many ionic and polar substances.

Question 18

Which of the following is a correct statement about isotopes?

Accepted Answer

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

Question 19

Which of the following best describes a hydrophobic interaction?

Accepted Answer

Nonpolar molecules aggregate together in water to minimize their exposure to water molecules.

Question 20

Which of the following best describes the relationship between [H$$^+$$] and pH?

Accepted Answer

As $$[H^+]$$ increases, pH decreases, according to $$pH = -\log [H^+].$$

Chemistry and Water: The Chemical Basis of Life

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