491. Polyprotic acids such as H3PO4, can act as acid-base buffers
A. only in combination with polyprotic bases
B. if their concentration is kept low
C. at pH values around neutrality
D. at pH values around any of their pKa’s

492. The pH of a solution is determined by
A. concentration of salt
B. relative concentration of acids and bases
C. dielectric constant of the medium
D. environmental effect

493. The reactions of molecules
A. are the reactions of the functional groups
B. are independent of the functional groups
C. require an enzyme in all cases
D. all of the above

494. Which of the following indicates that the pK of an acid is numerically equal to the pH of the solution when the molar concentration of the acid and its conjugate base are equal?
A. Michaelis-Menten equation
B. Haldanes equation
C. Henderson-Hasselbalch equation
D. Hardy-Windberg law

495. Molecules in which the atoms are held together by __________ bonds have the strongest chemical linkages.
A. noncovalent
B. covalent
C. ionic
D. hydrogen

496. Salt dissolves well in water as water molecules
A. form hydrogen bonds with the positively and negatively charged ions
B. make nonpolar covalent bonds with the positively charged ions only
C. surround the ions because of their charge but do not form hydrogen bonds
D. share electrons with the ions to make polar covalent bonds

497. Buffer solutions
A. will always have a pH of 7
B. are rarely found in living systems
C. cause a decrease in pH when acids are added to them.
D. tend to maintain a relatively constant pH.

498. A Bronsted acid becomes __________ upon losing a proton.
A. highly reactive
B. its conjugate acid
C. its conjugate base
D. a hydronium ion

499. Most of the important functional groups in biological molecules contain
A. oxygen and/or nitrogen and are acidic
B. oxygen and a phosphate
C. nitrogen and a phosphate
D. oxygen and/or nitrogen and are polar

500. What is the concentration, in moles/liter, of the hydrogen ion, if pH of a solution is 7?
A. 7
B. 7 x 10-7
C. 5 x 10-7
D. 1 x 10-7