by 4.74 1 90 ey s.3s 16 For ehe following feattiem, which ofthe fllowingisa pair

Question

by 4.74 1 90 ey s.3s 16 For ehe following feattiem, which ofthe fllowingisa pair listed as seid first, base r NO NO A010 M eous solution of an acid HA a pl of400 Whut is the vailue of &, 10s 10 10x 10 ) 10x 10 4) 10x 10 10x 10 I8. Which one of the following properties of solutions indicates an acidlic soluticn? ) plf- 10.09 (0]-2.5 10 M e)poH-3.68 d)[OH ]-1.7x10,A4 (on1-10x 10 19. The K, ofic lt,O, is 14x 10 What is K of the conjugate base CRO, a) 7.1x 10 b) 14x 10 )14x 10 i d) 14x 10 7.1x 10

Explanation / Answer

16. An acid has a tendency to loose a proton and the species formed after loosing a proton is called conjugate base of this acid. In the given reaction HNO2 is an acid , so the species formed NO2^-1 after loosing proton is it's conjugate base.

So the correct option is d)

17. The chemical equilibrium equation for the dissociation of the acid HA can be written as:

HA + H2O <-------------> A^-1 (aq) + H3O^+1(aq)

Ka for this can be written as:

Ka = [A^-1][H3O^+1]/([A^-1])

Using ICE table

[HA] . [A^-1]. [H3O^+1]

I 0.10 . 0 . 0

C. -x. x. x

E . 0.10 - x . x. x

As we know pH = -log [H3O^+1] ,So [H3O^+1] = 10^(- pH)

So, [H3O^+1] = 10^-4.00

So, x = [A^-1] = [H3O^+1] = 10^-4

So, Ka = (10^-4)(10^-4)/(0.10 - 10^-4) = 1.0 × 10^-7

So, the correct option is c)

18. For acidic solution pH should be less than 7 or acidic nature can be expressed in terms of [H3O^+1] or [OH^-1] . If [H3O^+1] concentration is greater than 10^-7 then solution is acidic (reverse will be for [OH^-1]

So only option b) show acidic character.

19. As we know Ka × Kb = Kw = 10^-14

So, Kb = (10^-14 ) / Ka = (10^-14) /(1.4 × 10 ^-4) = 7.1× 10^-11

So the correct option is a)

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