Which of the following is weakest acid?
Correct answer: A. HCN
- A. HCN
- B. NH₄⁺
- C. H₂S
- D. H₂CO₃
Explanation
HCN is the correct answer because it has the lowest dissociation constant (Ka) among the given options, indicating it is the weakest acid. NH₄⁺ is the conjugate acid of NH₃ and, while it can act as an acid, it is not generally compared to molecular acids like HCN, H₂S, or H₂CO₃ in terms of acidity strength. H₂S and H₂CO₃ are both weak acids but have higher dissociation constants than HCN, meaning they donate protons more readily and are thus stronger acids than HCN.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? support@testustad.com
About Acids, Bases and Salts
Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.
Practise Acids, Bases and Salts
314 free Acids, Bases and Salts MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Chemistry questions like this
Chemistry is on 14 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Acids, Bases and Salts questions
In acid base reaction, how many conjugate pairs are formed?
An acid-base reaction is the transfer of proton from an acid to a base. This is according to
Which of the following is amphoteric substance?
1.0 M solution of NaOH is mixed with 1.0 M solution of H₂SO₄+ the solution formed is:
Which of the following is not a base?
Which of the following is strongest Lewis base?