If a buffer solution is prepared from 5.15g #NH_4NO_3# and 0.10L of 0.15M #NH_3#, what is the pH of the solution?
It can be shown relatively easily that the
You have not quoted
Note that here I knew that volume of the solution was
PS I hope you can see the units in my calculations, because I can't! It is important that the dimensions in the log argument cancel out, which I think they do!
The ammonium ion is a weak acid and dissociates:
To find the
These are all equilibrium concentrations. We can set up an
For the initial moles of
The initial moles of
From the formula we can see that the initial moles of
Now we can set up the
Because the value of
Now we can put the numbers into
You will note I can use moles and not concentrations as the volume is common to both
This also accounts for any volume change when the solid salt is added to the solution.
In practice you could go straight to
This only works if