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Topic: Calculate the mass of KHP in an impure sample  (Read 340 times)

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Offline dude123

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Calculate the mass of KHP in an impure sample
« on: June 02, 2019, 02:52:12 AM »
If an impure KHP was in a solution, lets say 25ml and poured into a volumetric flask and filled to the 100ml mark with water. Then titrated against a 0.05M NaOH solution. For example, if it took 35ml to hit end point.
How would I calculate the actual mass of KHP in the initial impure KHP solution. I'm struggling to figure out the moles of KHP in the impure solution. Can you please outline the whole calculation though, thank you.

Offline Borek

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Re: Calculate the mass of KHP in an impure sample
« Reply #1 on: June 02, 2019, 03:37:03 AM »
Start with the reaction equation, then follow the stoichiometry.
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Offline dude123

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Re: Calculate the mass of KHP in an impure sample
« Reply #2 on: June 02, 2019, 05:34:26 AM »
Would I be right to say C1V1=C2V2? C2 being KHP concentration then n=cxv for the moles of KHP. Then times the moles calculated by 4 to get the original moles of impure KHP (from 25ml to 100ml) then m=nxmw for the g of pure KHP?

Offline Borek

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Re: Calculate the mass of KHP in an impure sample
« Reply #3 on: June 02, 2019, 06:43:12 AM »
That more or less contains all the necessary steps, although it is not clear to me whether the factor of 4 (for the 25 mL -> 100 mL) is a correct and necessary one. You had initially 25 mL of the solution, you diluted it four times - but you have never explained what part of 100 mL was titrated. All of that? Then you have titrated everything that was in the original 25 mL and you don't have to worry about dilution. Part of that? But what part?
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