Hello. I need help completing a lab about potentiometric titration of chloride i

ID: 519011 • Letter: H

Question

Hello. I need help completing a lab about potentiometric titration of chloride ions in an unknown.

I titrated as follows:

- Two separate beakers connected via voltmeter.

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BEAKER LEFT (100 mL soln)

1M KNO3 (100 mL distilled + 10 g KNO3)

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BEAKER RIGHT (100 mL soln)

0.7796 g of unknown transfered to 250 mL volumetric flask diluted. Took 25 mL of unknown from 250 flask + 75 mL water

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Buret filled with 0.0496 M of AgNO3

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I did the titration, and I got equivalence volume of 25.17 mL of AgNO3.

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Now I need to answer the following.

1. Mass of unknown in 25 mL aliquot: ______________

2. Avg vlm of AgNO3 : 25.17 mL

3. # of mols of Cl in 25 mL unknown soln : _______________

4. mass of Cl in 25 mL unknown soln: ______________.

5. %wt of chloride : ____________________.

I think the nernst equation is needed.

Here 1 mole of AgNO3 reacts with 1 mole of chloride ion,

At equivalence point,the no.of moles of silver nitrate is equivalent to the number of chloride ions present.

Equivalence volume=25.17 ml=0.02517mL

No of moles of silver nitrate present =0.02517( L)*0.0496(M)

=0.0012 moles

So no.of moles of chloride ion at equivalence point=0.0012

Molar weight of Chloride ion=35.453g

Therefore,mass of chloride ion present=0.0012*35.453

=0.0425g

So 25 ml of unknown solution contains 0.0425g of Chloride ions.So 250 ml will contain 0.425g of chloride ion.

So %wt of chloride=(0.425/0.7796)*100=54.5%

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