Question

Please answer all questions

Which of the following is NOT a strong acid? Select one: O a. H2S04 O b. HF O c. H Br O d. HNO3 о е. НСІ Calculate Ka for ammonium, NH4+. Select one: O a. 9.3 O b. 1.8 x 10-5 O c. 4.7 O d. 5.6 x 10-10 o e. 1.0 x 10-14

Answer 1

Answer – We are given the acids and asked for which is not a strong acid. A strong acid dissociates complete and gives 100 % hydronium ion, hence the K_a value for a strong acid is higher than one.

The weak acid is not dissociated completely, hence its K_a value is very small. The H₂SO₄ the first dissociation is higher than one. The HBr, HNO₃, and HCl are also K_a values higher than 1.

The acid HF is not strong acid since HF has a K_a value of 6.6 x 10^-4 that is very less.

Thus, HF is not a strong acid.

The Ka value for NH₄⁺ -

The K_b value for ammonia, NH₃ is 1.8 x 10^-5.

We know the relationship between the Ka and Kb is as follows,

The Ka value for NH₄⁺

Kw = Ka X K

The NH₄⁺ is the conjugate acid of ammonia,

        NH₃ + H₂O ----> NH₄⁺ + OH^-

The value for Kw is 1.0 x 10-14, so by plugging the values,

1.0 x 10-14 = KX 1.8 x 10-5

K 1.0 x 10-14 1.8 x 10-5 = 5.6 x 10-10

Thus, the Ka value for NH₄⁺ is 5.6 x 10^-10