| Which of the following is not a conjugate acid-base pair?
a) H2O , OH-
b)H2O, H3O
c) HSO-4, H2SO4
d) -OH, O2-
e) NO3-, NO2- | E |
| What is the conjugate acid of NH3?
A) +NH3
B) -NH
C) +NH4
D) -NH2
E) +NH2 | c |
| Give the conjugate acid and the conjugate base for HSO4-. | conjugate acid: H2SO4
conjugate base: SO4-2 |
| Write a completed equation for the acid-base pair shown below.
HCO2H + -NH2 → | HCO2H + -NH2 → HCO2- + NH3 |
| What is the conjugate acid of CH3NH2? | CH3NH3+ |
| What is the conjugate base of CH3NH2? | CH3NH- |
| What is the pH of a 0.1 M solution of HCl? (note: pKa for HCl is -6) | 1 |
| If the pH of a solution of HCl is 4.1, then what is the H3O+ concentration? | 7.9 × 10-5 |
| If H2O has a pKa value of 15.7 and HF has a pKa value of 3.2, which is a stronger base, HO- or F-? Explain. | HO- is a stronger base than F- because HF is a stronger acid than H2O, and the stronger the acid, the weaker its conjugate base. |
| How is the position of equilibrium determined in an acid-base reaction? | Compare the pKa value of the acid on the left side of the reaction arrow to the pKa value of the acid on the right side of the reaction arrow. The equilibrium favors reaction of the strong acid and formation of the weak acid. "Strong reacts to give weak". |
| Which of the following is the strongest acid? | CH3OH2+ |
| The pKa of CH3COOH is 4.8 and the pKa of HCOOH is 3.8. Given this information, one knows that __________. | HCOO- is a weaker base than CH3COO- |
| Which of the following statements is correct? | The stronger the acid, the weaker its conjugate base. |
| Which of the following is the strongest acid? | HF |
| Which of the following is the strongest acid? | CH3CH2OH |
| Explain why :NF3 is a weaker base than :NH3. | Fluorine has an electron withdrawing effect that reduces the availability of the pair of electrons on nitrogen. Thus the basicity of :NF3 is less than that of :NH3. |
| Consider the set of compounds, NH3, HF, and H2O. Rank these compounds in order of increasing acidity and discuss your rationale | NH3 < H2O < HF
When determining relative acidity, it is often useful to look at the relative basicity of the conjugate bases. The stronger the acid, the weaker (more stable, less reactive) the conjugate base. In this case, one would look at the relative basicity of F-, OH-, and NH2-. The relative strengths of these species can be gauged based on the electronegativity of the charged atom in each base. Since fluorine is the most electronegative, F- is the most stable, least reactive base in the group. This means that its conjugate acid, HF, is the strongest. |
| Would you predict trifluoromethanesulfonic acid, CF3SO3H, to be a stronger or weaker acid than methanesulfonic acid, CH3SO3H? Explain your reasoning. | Trifluoromethanesulfonic acid is a stronger acid. Compare the strengths of the conjugate bases and remember that the weaker the base, the stronger the conjugate acid. In the case of the trifluoro derivative, the presence of the highly electronegative fluorine atoms serves to delocalize the negative charge to a greater extent. This additional delocalization makes trifluoromethanesulfonate anion a weaker base. Also the electron withdrawing effect of the CF3 allows the proton to be more easily pulled off of the CF3SO3H molecule. |
| The pKa of CH3COOH is 4.8. If the pH of an aqueous solution of CH3COOH and CH3COO- is 4.8, then one knows | [CH3COOH] = [CH3COO-] |
| Explain why CH3CH2OH (pKa = 15.9) predominates in a solution of pH 4.5. | The pH of the solution is more acidic than the pKa of the OH group (15.9). A compound will mainly exist in its acidic form (with its proton) in solutions that are more acidic than the pKa value of the group that undergoes dissociation (pH is less than pKa). |
| When a small amount of hexanoic acid [CH3(CH2)4CO2H, pKa~4.8], is added to a separatory funnel which contains the organic solvent diethyl ether and water with a pH of 2.0, it is found mainly in the __________ phase as __________. | ether; CH3(CH2)4CO2H |
| When a small amount of hexanoic acid [CH3(CH2)4CO2H, pKa~4.8], is added to a separatory funnel which contains the organic solvent diethyl ether and water with a pH of 12.0, it is found mainly in the __________ phase as __________. | water; CH3(CH2)4CO2- |
| Which of the following is the definition of a buffer solution? | solution composed of a weak acid and its conjugate base AND solution that can maintain a nearly constant pH even with addition of small amounts of acid or base |
| Which of the following are Lewis bases? | NF3 & CH3OCH3 |
| What is meant by use of the following BENDING TO RIGHT arrow? | shows the movement from electron rich to electron poor & shows the movement of a pair of electrons |
| Explain why AlCl3 is a Lewis acid. | A Lewis acid is an electron pair acceptor. Aluminum in AlCl3 has an empty p orbital that can accommodate the pair of electrons provided by a Lewis base. |
| What is the product formed from the following acid-base reaction? | CH3OH (four dots/ two dots up two dots down)+ NH3(two dots next to N)= CH3O- + +NH4 |
| The conjugate acid of H2O is: | H3O+ (Two dots next to O) |
| Which of the following ions is the strongest acid? | H3O+ |
| Which species act as bases in the following reaction?
H2SO4+HNO3=H2NO3+ + HSO4-
1 2 3 4 | 2 and 4 |
