Biochem quiz 3

Which of the following is true about a molecule that is nonpolar?

• A. It has strong hydrogen bonds

• B. It has symmetrical charge distribution and equal sharing of electrons

• C. It has a high dipole moment

• D. It contains metal atoms

What determines the direction of the dipole moment in a polar covalent bond?

• A. The size of atoms

• B. The difference in electronegativity between bonded atoms

• C. The shape of the entire molecule

• D. The number of valence electrons only

Which of the following interactions is present in all substances regardless of polarity or type of atoms?

• A. Hydrogen bonding

• B. Van der Waals (dispersion) forces

• C. Ionic bonding

• D. Metallic bonding

In which type of bond is a dipole most likely to form?

• A. Metallic bond

• B. Polar covalent bond

• C. Non-polar covalent bond

• D. Ionic bond

What is required for a hydrogen bond to form?

• A. Two hydrogen atoms and one metal atom

• B. A hydrogen covalently bonded to a highly electronegative atom like O, N, or F

• C. A lone pair of protons

• D. Hydrogen sharing electrons equally with carbon

In a buffer solution, when the concentration of a weak acid is equal to the concentration of its conjugate base, what is true about the pH?

• A. pH = pKa

• B. pH = 7
  

• C. pH = 0

• D. pH = 14

According to the Henderson-Hasselbalch equation, when [A⁻] = [HA], what is the value of log([A⁻]/[HA])?

• A. 1

• B. 0

• C. -1

• D. Equal to Ka

Which of the following buffer solutions will have a pH equal to the pKa of the acid used?

• A. 0.3 M formic acid and 0.1 M sodium formate
  

• B. 0.2 M benzoic acid and 0.2 M sodium benzoate

• C. 0.1 M acetic acid and 0.5 M sodium acetate
  

• D. 0.5 M hydrochloric acid and 0.5 M sodium chloride

Which of the following statements about amino acids is TRUE?

• A. Amino acids act only as acids in aqueous solution.

• B. Amino acids act only as bases due to their amino group.

• C. Amino acids can act as both acids and bases depending on pH.

• D. Amino acids are neutral and do not interact with hydrogen ions.

Why are amino acids considered amphoteric?

• A. They have only basic groups.

• B. They can donate or accept protons because they contain both –COOH and –NH₂ groups.

• C. They have no charge at any pH.

• D. Their side chains are always non-polar.