The table below shows data for the and values for some acids and bases at 298 K.
| Acid | Ka | Base | pKb |
| C5H6OH | 1.02 x 10-10 | (C2H5)3N | 3.25 |
| O2NC6H4OH | 7.08 x 10-8 | C6H5NH2 | 9.13 |
Which two formulas represent the weakest acid and the weakest base in the table?
C5H6OH and C6H5NH2
O2NC6H4OH and C6H5NH2
O2NC6H4OH and (C2H5)3N
C5H6OH and (C2H5)3N
The ionisation constant of water, Kw , at 40 °C is 2.92 x 10-14. Which of the following statements is correct?
pH = 7.0
The ionisation of water is exothermic
The pH of water is lower at 40 °C than at 25 °C
[H+] > [OH-] at 40 °C
The Kb value for a base is 8.0 x 10-4 at 298 K. What is the pKa value for the conjugate acid at this temperature?
10
1.3 x 10-11
3.1
10.9
The pKb value of HPO42- is 6.8. What is its conjugate acid and what is the Ka value?
| Conjugate acid | Ka | |
| A. | H2PO4- | 7.2 |
| B. | H3PO4 | 7.2 |
| C | H3PO4 | 1.67 x 10-7 |
| D. | H2PO4- | 6.3 x 10-8 |
The strengths of four bases are:
What is the order of increasing base strength?
Ethanol < phenylamine < 3-nitrophenol < ethylamine
Ethanol < 3-nitrophenol < phenylamine < ethylamine
Ethylamine < 3-nitrophenol < phenylamine < ethanol
Ethylamine < phenylamine < 3-nitrophenol < ethanol
