Thread: Calculation of molarity - please help

Hi,

I have to make up a 0.5N solution of HNO3 (69%). I have attempted to do the calculation but am not confident if it is correct. Please see below:

no. moles = cv/1000

c = 0.5N v = 100ml

so no.moles = 0.5 x 100/ 1000 = 0.05 moles

mass = 0.05moles/63 = 3.15g

HN03 (69%) = 2.17g

Therefore 2.17g of HNO3 (69%) in 100ml water = 0.5N

Is this correct? (As someone else seems to have got 4.56g as the answer and I dont know where they obtained this from)

Thank you very much for any help.

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I did the calculations and got 4.56g.

This is where you went wrong: 69% * 3.15g = 2.17g

and 3.15g/69% = 4.56g.

So you multiplied where you should have divided. Try to determine why division is needed here.


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ok, thanks for your help.