make it easy for me to help you,
firstly what is your questions?
and can you at try and make your working a little more clear. I can make out that "n = c x v" is means "moles is concentration times volume" but i cant follow the rest of it.
50mL of 0.10mol/L hydrobromic acid is titrated with 0.10mol/l aqueous ammonia. Determine the pH at equivalence.
n=c x v
=0.10mol/L x 0.05L
NH4 + H2O --> NH3 + H3O
0.05 0 0
-x +x +x
0.05-x x x
I understand everything but how do u know that the Vtotal is 0.1L???
you need to look at the stiochemistry of the overall reaction, at equivalence you need to have one mole of the titre for ever mole of the substance your titrating. because they are both of the same concentration you will need the exact same volume of each to get the same number of mole of both of them.
in simple terms 0.05 + 0.05 = 0.1
had the concentration of the ammonia been 0.05mol/L you would have needed twice the volume hence the total volume in that case would be 0.05 + 0.1 = 0.15.
are you following ?