Question

Which is the strongest acid?

• A. CH\(_3\)-CH\(_3\)
• B. H\(_2\)O
• C. CH\(_2\)=CH\(_2\)
• D. CH\(_2\)

Hint:

Water (H\(_2\)O) is an amphoteric substance, meaning it can act as both an acid and a base, depending on the conditions.

Answer 1

The Correct Option is B

Acidity of a compound is determined by its ability to donate a proton (H\(^+\)). In the given options:
- CH\(_3\)-CH\(_3\) is an alkane and is very weakly acidic, typically acting as a base rather than an acid.
- CH\(_2\)=CH\(_2\) (ethylene) is an alkene, and while it is weakly acidic, its ability to donate a proton is much less than H\(_2\)O.
- H\(_2\)O (water) is the strongest acid among the options. It can ionize in water to produce H\(^+\) and OH\(^-\), making it a moderate acid with a pKa value of approximately 15.7.
- CH\(_2\) (formyl group) is not an acid, as it does not readily donate a proton in typical conditions.
Thus, the correct answer is (B) H\(_2\)O, as it is the strongest acid among the given options.