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Hi, just wondering could people here give me a hand on some of these. I've tried some of them and want to see if I'm right, and then there's one or two which I haven't got a clue how to answer, need some direction with. Thanks for any responses.


Q. Magnesium hydroxide and sulphuric acid react in water to give compound A. TG analysis of A was undertaken.

Gentle heating at approximately 100 ºC results in 2 mass losses. The remaining mass after the first event is 56.1% and after the second event it is 48.8%. A third event, after extreme heating in excess of 300 ºC, is seen, after which the mass remaining is 16.40 %. Identify A, and write a balanced equation for its formation. Write balanced equations for all three events observed in the TG experiment.

[Atomic masses: H = 1.01, O = 16.00, Mg = 24.31 and S = 32.06]


Haven't the foggiest how to do the above, tried googling for help and still unsure.


Q. Injected solvent passes through a chromatographic column in 2.0min while two drug substances require 6.0 and 10.0min respectively. Calculate the capacity factors k' for the two solutes. What is the selectivity of the separation?


k'A = t R - tM / tM <-- I think this equation is used but am unsure...tm/tm do you just put 6 in for both top and bottom?


and I think this equation is used for the selectivity;


a = k 'B / k 'A but can't answer that until I do the top half which I'm sort of unsure of as well.



Q. A chromatogram shows an eluted solute peak, with ideal Gaussian shape at Tr = 10.0min and w1/2= 1.0min.


(i) How many theoretical plates are present?

(ii) Find the plate height if the column is 10cm long?


This is my attempt at that...


N = 5.54[tr/ w1/2]^2


55.4 theoretical plates present


HETP = L/N... 100mm/55.2 ==> 1.81


So can anyone help with these three questions and correct my if I said or made an error above.



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