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### Topic: Titration with multiple end points question.  (Read 1335 times)

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#### Frustratedstudent

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##### Titration with multiple end points question.
« on: May 03, 2017, 05:22:43 AM »
Hi guys, so currently have an assignment to hand in and the teacher is being zero help, just saying we need to work everything out ourselves, but not explaining in any way how to go about calculating it. The question is:

A 50 cm3 solution, labelled batch X, containing a mixture of sodium carbonate and sodium hydrogencarbonate was titrated wiith 0.18 mol/dm3 hydrochloric acid solution. The results produced an EP1 = 15. 37 cm3 and an EP2 = 38.29 cm3

Using the titration results, calculate the  % w/v sodium carbonate and the % w/v sodium hydrogencarbonate present in the batch X.

I don't understand
a) how to calculate this
b) what impact the two endpoints have and how they are used to calculate this
c) how I then calculate the % w/v of each part from the information.

I just don't get what I'm supposed to do. Please, my deadline is looming bad and I've had such a hard time with this one damned question, any help would be so monumentally appreciated <3

#### DrCMS

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##### Re: Titration with multiple end points question.
« Reply #1 on: May 03, 2017, 06:20:33 AM »
What happens when sodium carbonate reacts with a small amount of acid?
What happens when is reacts with excess acid?
What reaction does the 1st endpoint match?
What reaction does the 2nd endpoint match?

#### Frustratedstudent

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##### Re: Titration with multiple end points question.
« Reply #2 on: May 03, 2017, 06:49:13 AM »
I'll try and scratch away at those (I'm a student doing a course preparing for a nursing degree, so it's all biology and then suddenly titration paper out of absolutely nowhere, we haven't looked at weak or excess reactions, not covered remotely).

#### Borek

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##### Re: Titration with multiple end points question.
« Reply #3 on: May 03, 2017, 12:42:19 PM »
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info, PZWT_s1