Quote Originally Posted by exo_body
hey man, the first one you did was wrong sorry. the equation is:
NaOH + H3PO4 -> NaH2PO4 + H20
now using the details of H3PO4
conc: 0.2 0.22
vol: 250/1000
moles: =0.22*(250/1000) (therefore, as its a 1:1 reaction, theres the same number of moles of NaOH)

now to work out the volume, you use the equation volume = moles/volume

so [0.22*(250/1000)] 0.2
will give you 0.275dm^-3, then just multiply by 1000 to get the answer in cm^-3

hope thats any help, i think its right. do you want the others done? they follow the same kinda pattern, but they seem slightly easier. well question 2 does.
I did chemistry at school so I can say this with confidence (although I'll admit I totally failed), those answers are right.