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# Titration Question Help URGENT (A-Level & Advanced Chemistry) Watch

1. I have homework due tomorrow for chemistry and I was wondering whether someone could help me with a question that im stuck on.

Overall Equation:
6S2O3^2- + BrO3- + 6H+ ---> 3S4O6^2- + Br- + 3H2O

Question:

''A laboratory technician decided to use a 5.00 x 10^3 mol dm^-3 solution of sodium bromate (V) to check the concentration of a sodium thiosulfate solution that was labelled 1.00 x 10^-3 mol dm^-3. The sodium bromate (V) solution was placed in the burette and 25,0 cm^3 of the sodium thiosulfate solution was pipetted into a conical flask.

Use the concentration of the sodium thiosulfate solution to calculate the expected titre value of this experiment''

Its quite urgent so it would be great if someone could tell me the answer and how they got it, thanks!

---------
charco could you help?
2. Anyone??
3. (Original post by qwerty123A)
I have homework due tomorrow for chemistry and I was wondering whether someone could help me with a question that im stuck on.

Overall Equation:
6S2O3^2- + BrO3- + 6H+ ---> 3S4O6^2- + Br- + 3H2O

Question:

''A laboratory technician decided to use a 5.00 x 10^3 mol dm^-3 solution of sodium bromate (V) to check the concentration of a sodium thiosulfate solution that was labelled 1.00 x 10^-3 mol dm^-3. The sodium bromate (V) solution was placed in the burette and 25,0 cm^3 of the sodium thiosulfate solution was pipetted into a conical flask.

Use the concentration of the sodium thiosulfate solution to calculate the expected titre value of this experiment''

Its quite urgent so it would be great if someone could tell me the answer and how they got it, thanks!

---------
charco could you help?
TSR policy is not to do homework, rather to give hints.

You have the stoichiometric equation, this tells you how many moles of bromate react with moes of thiosulfate (in this case 1:6)

Moles = molarity x volume

and you know the 'expected' molarity of the sodium thiosufate and the actual volume, so you can calculate the 'expected' moles.

From the stoichiometeric equation you can see that if you divide by 6 you get the expected moles of thiosulfate.

.. and you know that moles = molarity x volume

so you can calculate the expected volume.
4. (Original post by charco)
TSR policy is not to do homework, rather to give hints.

You have the stoichiometric equation, this tells you how many moles of bromate react with moes of thiosulfate (in this case 1:6)

Moles = molarity x volume

and you know the 'expected' molarity of the sodium thiosufate and the actual volume, so you can calculate the 'expected' moles.

From the stoichiometeric equation you can see that if you divide by 6 you get the expected moles of thiosulfate.

.. and you know that moles = molarity x volume

so you can calculate the expected volume.
Thanks! Can you atleast tell me whether my answer of 0.834cm^3 is correct?
5. (Original post by qwerty123A)
Thanks! Can you atleast tell me whether my answer of 0.834cm^3 is correct?
A laboratory technician decided to use a 5.00 x 10^3 mol dm^-3 solution of sodium bromate (V) to check the concentration of a sodium thiosulfate solution that was labelled 1.00 x 10^-3 mol dm^-3. The sodium bromate (V) solution was placed in the burette and 25,0 cm^3 of the sodium thiosulfate solution was pipetted into a conical flask.

Use the concentration of the sodium thiosulfate solution to calculate the expected titre value of this experiment
First of all I am assuming that the concentration of the bromate is a typo and it should be 5.00 x 10^-3

25ml of 0.001M sodium thiosulfate contains 0.025 x 0.001 mol = 2.5 x 10-5 mol

From the equation 6 mol of thiosulfate reacts with 1 mol of bromate.

So, mol bromate = 2.5 x 10-5/6 = 4.17 x 10-6

Molarity of bromate = 5 x 10-3

mol = molarity x volume

volume = mol/molarity = 4.17 x 10-6/5 x 10-3 = 0.833 ml

Which is, IMHO, a stupid answer to a question ...

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Updated: March 10, 2016
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