Question

4 mole of NH4OH and 1 mole of H2SO4 are
mixed and diluted to 1 lit. pKb of NH4OH is
4.8. The pH of the solution is
1)9.2 2) 4.8 3) 9.8021 4) 4.1979​

Answer 1

Answer:

When 4 moles of NH4OH and one mole  of H2SO4 are mixed and diluted to 1 litre solution and the pkb of ammonium hydroxide is given as 4.8 so to determine the kb go as follows;

kb= 10^-pkb

kb= 10^ -4.8

= 1.58 x 10^-5

therefore to determine degree of dissociation from kb, follow this;

kb = C∝²

where C is the concentration and ∝ is the degree of dissociation

1.58 x 10^-5 = 4∝²

∝ = 1.99 x 10^-3

then determine the equillibrium concentration of hydroxyl ions

[OH-] = C∝

[OH-] = 4 x (1.99 x 10^-3)

          = 7.96 x 10^-3

so finally get the pOH= -log 7.96 x 10^-3

pOH= 2.1

Hence pH= 11.9.