tssm exam

[cootcoot]

Question 1
A 20.0 mL sample of acid is delivered to a laboratory for analysis. The identity of the acid,
and its concentration, is not known. The 20.0 mL sample is made up to the mark with water in
a 250 mL volumetric flask.
25 mL aliquots are then titrated against 0.05 M sodium carbonate, Na2CO3 solution. Methyl
red is chosen as the indicator and a sharp transition occurs at an average titre of 15.6 mL.
a. Calculate the number of mole of Na2CO3
____________________________________________________________________
1 mark
b. Complete the table, showing possible concentrations of the acid.
If the acid is:                            concentration of diluted acid                concentration of original acid
                      Monoprotic
                      Diprotic
                      triprotic
3 marks



how does one do part b may i ask?

[polky]

Try writing out equations using common monoprotic/diprotic/triprotic acids as your acid, for example HCl, H2SO4 and H3PO4.  Then you can find the mole ratios and then find the concentrations.

Hope that helps! I might post a better solution later when I have time xD

[cootcoot]

ahhh,i see. it did help!
thanks for that!

[Glockmeister]

yeah, i cocked question up too... and I had all the skills to do it too