Arrange the acids
I) hydrogen selenate ion (HSeO−
4
),
pKa = 1.92;
II) phosphorous acid (H3PO3),
pKa1 = 2.00;
III) phosphoric acid (H3PO4), pKa = 2.12;
IV) selenous acid (H2SeO3), pKa = 2.46;
in increasing order of strengths.
1. IV, III, II, I
2. II, IV, III, I
3. I, III, II, IV
4. I, III, IV, II
5. IV, II, III, I
6. None of these
7. III, IV, II, I
8. I, II, III, IV
9. Cannot be determined
10. I, II, IV, III
pk of 1 is stronger than pk of 2 is stronger than pk 9, etc. That should make it easy to arrange.
To arrange the acids in increasing order of strengths, we need to compare their respective pKa values. The lower the pKa value, the stronger the acid.
The correct answer is 4. I, III, IV, II
Let's compare the pKa values:
I) Hydrogen selenate ion (HSeO−4): pKa = 1.92
II) Phosphorous acid (H3PO3): pKa1 = 2.00
III) Phosphoric acid (H3PO4): pKa = 2.12
IV) Selenous acid (H2SeO3): pKa = 2.46
Based on the pKa values, the correct order of strengths from weakest to strongest is:
I) Hydrogen selenate ion (HSeO−4): pKa = 1.92
III) Phosphoric acid (H3PO4): pKa = 2.12
IV) Selenous acid (H2SeO3): pKa = 2.46
II) Phosphorous acid (H3PO3): pKa1 = 2.00
So, the correct answer is 4. I, III, IV, II.
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.
First, let's compare the pKa values for each acid:
I) Hydrogen selenate ion (HSeO−4), pKa = 1.92
II) Phosphorous acid (H3PO3), pKa1 = 2.00
III) Phosphoric acid (H3PO4), pKa = 2.12
IV) Selenous acid (H2SeO3), pKa = 2.46
Comparing the pKa values, we can see that the order from lowest to highest is:
1) Hydrogen selenate ion (HSeO−4), pKa = 1.92
2) Phosphorous acid (H3PO3), pKa1 = 2.00
3) Phosphoric acid (H3PO4), pKa = 2.12
4) Selenous acid (H2SeO3), pKa = 2.46
Therefore, the correct option is 1. IV, III, II, I.