Now I can set up the Kb expression.

Kb, equal to the NH4 plus concentration

times the Minus concentration

divided by NH3 Concentration.

The water is omitted from our Kb expression because it's a pure liquid.

I now plug in the values I know, which are the Kb value is 1.8 x 10 to the -5.

And if that's not given, that's a value you can generally look up.

I have x for my NH4+ concentration, x for my Concentration and

0.150- X for the NH3 concentration.

Now I'm going to make the assumption that x is much, much less than 0.150.

This will allow me to simplify the expression

to 1.8 x 10 to the -5 equals x squared over 0.150.

Now I can solve for x, and

x=1.6 times 10 to the minus 3.

This will my hydroxide concentration.

I also see that the value of x is only about 1% of the value of 0.150.

So my assumption was valid.

And I can find my hydroxide concentration just by using the value of X.

It will also be the concentration of NH4+ since those two concentrations are equal.