Arrange the acids
I) hydrogen selenate ion (HSeO−
4
),
pKa = 1.92;
II) phosphoric acid (H3PO4), pKa = 2.12;
III) selenous acid (H2SeO3), pKa = 2.46;
IV) phosphorous acid (H3PO3),
pKa1 = 2.00;
in increasing order of strengths.
1. I, III, II, IV
2. None of these
3. I, III, IV, II
4. II, IV, III, I
5. III, II, IV, I
6. IV, II, III, I
7. I, II, IV, III
8. Cannot be determined
9. I, IV, II, III
10. III, IV, II, I
pKa goes from weak acid to strong acid as the number goes down; i.e., pKa 2 is a stronger acid than pKa 5 which in turn is stronger than a pKa of 9.
You can arrange them with that information.
To arrange the acids in increasing order of strengths, we need to compare their pKa values. The lower the pKa value, the stronger the acid. Let's compare the pKa values:
I) hydrogen selenate ion (HSeO−4), pKa = 1.92;
II) phosphoric acid (H3PO4), pKa = 2.12;
III) selenous acid (H2SeO3), pKa = 2.46;
IV) phosphorous acid (H3PO3), pKa1 = 2.00;
Based on the given pKa values, we can arrange the acids in increasing order of strengths:
9. I, IV, II, III
Therefore, the correct answer is option 9.
To arrange the acids in increasing order of strengths, we need to compare their pKa values. The lower the pKa value, the stronger the acid.
Given the pKa values:
I) hydrogen selenate ion (HSeO−4), pKa = 1.92
II) phosphoric acid (H3PO4), pKa = 2.12
III) selenous acid (H2SeO3), pKa = 2.46
IV) phosphorous acid (H3PO3), pKa1 = 2.00
Comparing the pKa values, we can see that the correct order is:
1. I, III, II, IV
Explanation:
- Hydrogen selenate ion (HSeO−4) has the lowest pKa value of 1.92, making it the strongest acid.
- Selenous acid (H2SeO3) has a pKa of 2.46, which is higher than HSeO−4, so it is the next in line.
- Phosphoric acid (H3PO4) has a pKa of 2.12, higher than both HSeO−4 and H2SeO3.
- Phosphorous acid (H3PO3) has a pKa of 2.00, which is the highest among the given acids.
Therefore, the correct answer is option 1. I, III, II, IV.