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Quiz: Water, pH, and Organic Chemistry

Test your understanding of Chapter 2 concepts.

1. Why is a water molecule polar?

  1. Oxygen and hydrogen share electrons equally
  2. Oxygen is more electronegative, creating partial charges
  3. Hydrogen has more electrons, giving it a negative charge
  4. Both atoms have identical electronegativities
Show Answer

The correct answer is B. Oxygen attracts the shared electrons more strongly, giving oxygen a partial negative charge and hydrogens partial positive charges (Water Structure section).

Concept Tested: Water polarity

2. Which property allows water to moderate temperature in organisms and environments?

  1. Low specific heat
  2. High surface tension
  3. High specific heat
  4. Low heat of vaporization
Show Answer

The correct answer is C. Water absorbs or releases large amounts of heat with only slight temperature change, stabilizing climates and body temperatures (Water Properties section).

Concept Tested: Specific heat

3. A solution has [H⁺] = 1 × 10⁻⁸ M. What is its pH?

  1. 6
  2. 7
  3. 8
  4. 9
Show Answer

The correct answer is C. pH equals –log[H⁺]; –log(10⁻⁸) = 8, making the solution slightly basic (pH scale discussion).

Concept Tested: Calculating pH from [H⁺]

4. Which buffer reaction describes how blood resists drops in pH when CO₂ accumulates?

  1. HCO₃⁻ + H⁺ → H₂CO₃
  2. CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻
  3. H₂CO₃ → CO₂ + H₂O
  4. H⁺ + OH⁻ → H₂O
Show Answer

The correct answer is B. Carbon dioxide reacts with water to form carbonic acid, which dissociates to buffer excess protons (Carbonic acid–bicarbonate buffer section).

Concept Tested: Buffer chemistry

5. Why can carbon form diverse organic molecules?

  1. It has two valence electrons
  2. It forms four covalent bonds due to four valence electrons
  3. It only forms ionic bonds with metals
  4. It is highly electronegative and attracts electrons
Show Answer

The correct answer is B. Carbon’s tetravalence allows formation of four covalent bonds, producing varied skeletons and functional groups (Carbon backbone section).

Concept Tested: Carbon tetravalence

6. Which statement about carbon skeletons is true?

  1. They must be linear chains without branching
  2. Double bonds cannot occur in carbon chains
  3. They can be straight, branched, or form rings
  4. Carbon skeletons always contain oxygen atoms
Show Answer

The correct answer is C. Chapter 2 highlights straight, branched, ringed, and double-bonded skeletons, explaining the diversity of organic molecules.

Concept Tested: Carbon skeleton diversity

7. Which functional group acts as an acid by donating H⁺ to solution?

  1. Amino (–NH₂)
  2. Carbonyl (C=O)
  3. Carboxyl (–COOH)
  4. Methyl (–CH₃)
Show Answer

The correct answer is C. The carboxyl group can release the hydrogen from its hydroxyl portion, lowering pH (Functional groups table).

Concept Tested: Functional group behavior

8. What happens to pH when a base is added to pure water?

  1. pH decreases because [H⁺] increases
  2. pH increases because [H⁺] decreases
  3. pH remains 7 regardless of additions
  4. [OH⁻] decreases causing lower pH
Show Answer

The correct answer is B. Bases reduce free hydrogen ion concentration by accepting H⁺ or releasing OH⁻, thus raising pH (Acids and bases section).

Concept Tested: Effect of bases on pH

9. Dehydration synthesis differs from hydrolysis because dehydration synthesis __.

  1. Adds water to split polymers
  2. Removes water to build polymers
  3. Produces monomers only
  4. Occurs only in lipids
Show Answer

The correct answer is B. Dehydration removes water between monomers to form covalent bonds, while hydrolysis adds water to break them (Macromolecule preview).

Concept Tested: Polymerization reactions

10. Why does water exhibit cohesion?

  1. Hydrophobic interactions between molecules
  2. Hydrogen bonds linking adjacent molecules
  3. Ionic bonds between oxygen and hydrogen
  4. Metallic bonding across liquid water
Show Answer

The correct answer is B. Hydrogen bonding causes water molecules to stick together, enabling phenomena like surface tension (Cohesion section).

Concept Tested: Cohesion via hydrogen bonding