Question

Consider a binary acid, represented as HA, in which one or more ionizable H atoms are bonded to one additional element. HA is not an oxoacid. Which of the following statements correctly summarize the influence of partner A on the strength of the acid HA? Choose one or more:

HA becomes more acidic as the number of ionizable H atoms in the structure increases.

For partner atoms in the same group, HA becomes more acidic as A increases in size.

HA will always become more acidic as the electronegativity of A increases.

HA becomes more acidic as the partner atom A becomes more metallic.

For partner atoms in the same period, HA will become stronger as A becomes smaller.

Answer 1

Ans :- Following are the correct statements :-

(b) For partner atoms in the same group, HA becomes more acidic as A increases in size.

(e) For partner atoms in the same period, HA will become stronger as A becomes smaller.

Explanation :-

Correct statements :-

(b) For partner atoms in the same group, HA becomes more acidic as A increases in size , because down the group strength of H-A bond decreases as size of A increases therefore release of H⁺ becomes easier. Hence acidic strength increases down the group.

For e.g:- Increasing order of acidic strength of hydrides of halogens as :

HF < HCl < HBr < HI

(e) For partner atoms in the same period, HA will become stronger as A becomes smaller , because left to right in the period atomic radii decreases therefore strength of HA increases.

For e.g :- Increasing order of stability of the hydrides of group-15, group-16 and group-17 as :

NH₃ < H₂O < HF

Incorrect statements :-

(c) HA will always become more acidic as the electronegativity of A increases is incorrect, because as the electronegativity of A increases acidic strength decreases.

For e.g :- HF is less acidic than HI but F is more electronegative than I.

(a) HA becomes more acidic as the number of ionizable H atoms in the structure increases is incorrect, because acidic strength always depends upon the release of first ionizable hydrogen.

For e.g :- HF (having one ionizable H) is a acid while H₂O (having two ionizable H) is neutral.

(d) HA becomes more acidic as the partner atom A becomes more metallic is incorrect because hydrides of metals are basic in nature while hydrides of non-metals are acidic.

For e.g :- NaH is basic while HF is acidic.