Refer to Equilibrium Constants. Calculate the pH of a solution resulting from the addition of 50.0 mL of 0.30 M HNO3 to 50.0 mL of 0.30 M NH3.

Answer 1

After addition, all of the NH3 becomes NH4^+ and the pH is determined by dissociation of H^+.

NH4^+ -----------------> NH3 + H^+

Calculate new molarity after addition of acid.

Molarity of NH4^+=(0.3M*0.050L)/(0.100L)=0.15M

I......0.15 M...................0............0
C......-X.............,.......+X..........+X
E.....0.15 M-X..............X...........X

Kw/Kb=Ka=[products]/[reactants]

Ka=[x][x]/[0.15M-x]

5% dissociation allows for simplification....

Ka=x^2/[0.15M]

X=√(Ka*0.15M)

pH=-log[x]

Answer with the correct number of significant figures and.check 5% dissociation.