calculate the % of each of thes two forms of nitrogen in the wastewater?

Question

Total ammonia nitrogen in waste water discharges comprises ammonia nitrogen (NH3-N) and ammonium nitrogen(NH4+-N). If pH and temperature of the wastewater discharge are 8 and 25degC, calculate the % of each of thes two forms of nitrogen in the wastewater. K is 1.82 EXP -5

Answer 1

First, you wrote K wrongly. 1.82 EXP -5 means: 1.82 times e to the power of (-5), where e is the base of natural logarithm and e = 2.718281828459045....
A correct way to write K is: K = 1.82x10^-5, or simply in the format of some computer database: K = 1.82e-5.
Now come to the chemistry part.
There is a balance: NH4+ <==> H+ + NH3, Ka = 1.82e-5
Since pH is given, we have: [H+] = 10e-8 M.
Hence: Ka = 1.82e-5 = [H+]*[NH3] /[NH4+] = 10e-8*[NH3] /[NH4+]
or 1.82e+3 = [NH3] /[NH4+]
So the % of NH3 is: [NH3] /{[NH3] + [NH4+]} = 1.82e+3/(1+1.82e+3) = 99.945%
and the % of NH4+ is: [NH4+] /{[NH3] + [NH4+]} = 1/(1+1.82e+3) = 0.055%