Hi, Q: A solution of volume 0.500 contains 1.68g NH3 and 4.05g (NH4)2SO4. find the pH of the solution. I got 9.76 but that's incorrect and I have no idea what to do here's my work so I converted NH3 and (NH4)2SO4 into moles and divided them by 0.500L so the concentration of [NH3]=0.19718M and [(NH4)2SO4]=0.0613M then I used an ice table NH3 + H2O NH4 + OH kb=1.8x10^-5 0.19718 0.061289 -x +x +x 0.19718-x 0.061289+x x kb=x(0.061289+x)/0.19718-x kb

Question

Hi,
Q: A solution of volume 0.500  contains 1.68g NH3  and 4.05g  (NH4)2SO4.
find the pH of the solution.

I got 9.76 but that's incorrect and I have no idea what to do 

here's my work 
so I converted NH3 and (NH4)2SO4 into moles and divided them by 0.500L so the concentration of [NH3]=0.19718M and [(NH4)2SO4]=0.0613M
then I used an ice table

NH3 +   H2O <--> NH4 +       OH  kb=1.8x10^-5
0.19718                 0.061289
-x                             +x              +x
0.19718-x             0.061289+x   x 

kb=x(0.061289+x)/0.19718-x   

kb<<<<0.061289 and 0.19718

anonymous · Answer

kb=0.061289x/0.19718

x=1.0x10^-9

x is the concentration of OH 
pH=-log(1.0x10^-14/1.0x10^-9)=9.76