alleryStart learning →For a diprotic acid, how do the two ionisation steps compare?
AThe two steps proceed to an equal extent
BThe second step proceeds further than the first
CThe two steps occur at the very same instant
DThe first step proceeds further than the second
Answer & Solution
Correct answer: D. The first step proceeds further than the second
1. A diprotic acid carries two ionisable hydrogen atoms per molecule.
2. They are lost one after the other, not together.
3. The first proton leaves a neutral or less negative species, so it goes more easily.
4. The second must leave an already negative ion, which holds it more tightly.
5. So the first ionisation always proceeds to a greater extent than the second.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 14 "Acid-Base Equilibria", section 14.5 Polyprotic Acids_
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