How to calculate initial concentration

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SUMMARY

The discussion focuses on calculating the initial concentration of methylamine (CH3NH2) after titration with hydrochloric acid (HCl). The user correctly calculated the moles of HCl as 0.0025 moles using the formula n = cv, where c is the concentration and v is the volume in dm³. The initial concentration of methylamine was determined to be 0.05 mol/dm³ by dividing the moles of HCl by the volume of the methylamine solution used (50.0 cm³). The endpoint of the titration was noted to occur at 25 mL of added acid.

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Homework Statement


A known mass of methylamine, CH3NH2, was dissolved in water at 25 celsius

50.0 cm^3 of this solution was taken and titrated with 1.00x10^-1 mol dm^-3 hydrochloric acid solution, HCL(aq). The change in pH as an increasing volume of hydrochloric acid was added is shown in the graph below: (Didn't scan the graph)

Homework Equations


These are the equations I think are relevant.
n=m/Mr
n=cv

The Attempt at a Solution


I'm quite lost at what to do from here so help would be appreciated.
 
Last edited:
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Is this right? If so, I'm ashamed of meself.

moles HCl=0.1x0.025=0.0025
Initial concentration CH3NH2=0.0025/0.05=0.05
 
your working seems correct, given that the endpoint of the titration was at 25 mL added acid. Remember that we do not have access to the unscanned pH curve for the titration.

The other point that I would take issue with is that it would be a good idea to show a few units in your answer, and maybe even in your working.
 

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