Buffer is composed of weak acid and its conjugate base or weak base and it is conjugate acid. so The correct answer is:
0.21 M hydrofluoric acid + 0.20 M potassium Fluoride
due to the first choice contain NaOH which is strong base not weak
second choice both salts no acid or base
Third choice contain HNO₃ which is considered as strong acid
Fourth choice contain ammonia but without its conjugate acid like (NH₄Cl for example) instead it has different salt
Fifth Choice contain HF which is weak acid and KF which is its conjugate base so this is the correct one
B nonmetals that’s your answer :)
The first solution or a I think is the correct answer
Answer:
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