F.4 Chem Question (alkalis)

First, caustic does not mean concentrated.

In stead, it means "corrosive".

Strong alkali is corrosive, from the above choices given to you,

only potassium hydroxide and sodium hydroxide are strong alkali.

Therefore, the answer should be C.

Note: To see whether the alkali is corrosive, you should check whether it is a strong alkali or a weak one. If the alkali is strong, you could say that is caustic. It DOES NOT depends on the concentration (i.e. concetrated / diluted).


For ammonoia solution, since it is a weak alkali (i.e. partially ionizes in water), we say that it is "irritant".




Hope my explanations help.

The answer is C. (1) and (3).

"Caustic" usually refers to the corrosive property of strong alkalis.

(1) is correct.
Potassium hydroxide is a strong alkali, and its common name is "caustic potash".

(2) is incorrect.
This is because ammonia is a weak alkali.

(3) is correct.
Sodium hydroxide is a strong alkali, and its common name is "caustic soda".

I think the ans. is (1) and (3)

It is because caustic means strong;
the solution is completely ionizied.
And K+ and Na+ can competely ionized!
but NH4+ is weat, it is slightly ionized in water

Hope I can help u