Chapter 2: Water, Acids, and Bases

General Biochemistry

Which intermolecular force is the weakest?

a. Hydrogen bonding

b. Ion-dipole interactions

c. London dispersion

d. Dipole-dipole interactions

c. London dispersion

In a hydrogen bond, the hydrogen atom is covalently bonded to a(n):

a. Carbon

b. Metal ion

c. Electronegative atom like N, O, or F

d. Halogen atom like Cl or Br

c. Electronegative atom like N, O, or F

Why is water considered the solvent of life?

a. It is nonpolar and cannot dissolve ions

b. It is amphipathic

c. It is highly polar and forms hydrogen bonds

d. It has a low dielectric constant

c. It is highly polar and forms hydrogen bonds

Antifreeze proteins protect organisms in cold environment by:

a. Lowering the pH of water

b. Binding ice crystals to prevent growth

c. Increasing hydrophobic interactions

d. Preventing water from autoionizing

b. Binding ice crystals to prevent growth

Which of the following molecules is amphipathic?

a. Glucose

b. Phospholipid

c. NaCl

d. Cholesterol

b. Phospholipid

What is the pH of pure water at 25°C?

a. 0

b. 7

c. 14

d. Depends on concentration of salts

b. 7

If the pH is 9 and the pKa of a weak acid is 7, which form dominates?

a. Protonated form (HA)

b. Deprotonated form (A⁻)

c. Equal concentrations of HA and A⁻

d. Cannot be determined

b. Deprotonated form (A⁻)

Which statement is correct about protonation and solubility?

a. Protonated molecules are always more soluble

b. Deprotonated (charged) molecules are more soluble in water

c. Protonation state has no effect on solubility

d. Deprotonated molecules cannot hydrogen bond

b. Deprotonated (charged) molecules are more soluble in water

According to the Brønsted–Lowry definition, a base is:

a. A proton donor

b. A proton acceptor

c. An electron pair donor

d. An electron pair acceptor

b. A proton acceptor

In the reaction HCl + H₂O → H₃O⁺ + Cl⁻, what is the conjugate base?

a. H₂O

b. H₃O⁺

c. HCl

d. Cl⁻

d. Cl⁻

Which acid has the highest strength?

a. pKa = 10

b. pKa = 4

c. pKa = 6

d. pKa = 8

b. pKa = 4

A buffer works best when:

a. pH ≫ pKa

b. pH ≈ pKa

c. pKa ≫ pH

d. There is no conjugate base present

b. pH ≈ pKa

Which buffer system maintains blood pH around 7.4?

a. Phosphate buffer system

b. Ammonia buffer system

c. Carbonic acid-bicarbonate buffer

d. Histidine buffer

c. Carbonic acid-bicarbonate buffer

If blood pH drops below 7.35, this condition is called:

a. Alkalosis

b. Acidosis

c. Buffering

d. Neutralization

b. Acidosis

In the carbonic acid-bicarbonate buffer system, what physiological mechanism removed CO₂ to help maintain pH?

a. Liver metabolism

b. Kidney reabsorption

c. Exhalation by the lungs

d. Protein denaturation

c. Exhalation by the lungs