Chemistry Quesiton - Bleach Titration

zodac

Yeah, for this experiment, how do you find out the dilution factor? In "Chemistry Live!" they have an example, and they multiply the moles/l by 10 to get the "original conecntration".

How do you get that value?

celtic723

zodac wrote: »

Yeah, for this experiment, how do you find out the dilution factor? In "Chemistry Live!" they have an example, and they multiply the moles/l by 10 to get the "original conecntration".

How do you get that value?

if they use 25cm^3 of bleach just always remember that it's a times 10 dilution and whatever moles you get for the undiluted bleach x 10 to get the undiluted.

ironclaw

Say your have 25cm cubed of bleach and you put it in a 500cm volumetric flask which you then fill with water, you have diluted the bleach 20 times

i.e. Thats 500cm divided by 25.

celtic723 wrote: »

if they use 25cm^3 of bleach just always remember that it's a times 10 dilution and whatever moles you get for the undiluted bleach x 10 to get the undiluted.

Careful, the question can change. There is nothing to say they could use 75cm of bleach and dilute it to 800cm or similar. The dilution faction dones't have to be, but normally is, a whole number.

almostnever

Divide the final volume of the bleach solution by the volume of actual bleach used in the solution to get the dilution factor,if that makes sense. I am so bad at explaining things!

monkseyz

the example in your book uses 25cm^3 of bleach and they dilute up to 250cm with deionised water. The dilution factor therefore is 10 ie. x10

if it had been made up to 500 cm then the dilution factor would be 20. so divide the amount you made it up to by the amount of bleach used ie 250 * 25 = 10

zodac

celtic723 wrote: »

if they use 25cm^3 of bleach just always remember that it's a times 10 dilution and whatever moles you get for the undiluted bleach x 10 to get the undiluted.

Is that because they use 250cm^3 or the value is always 10?

zodac

Ok thanks, that clears that section up.

celtic723

ironclaw wrote: »

Say your have 25cm cubed of bleach and you put it in a 500cm volumetric flask which you then fill with water, you have diluted the bleach 20 times

i.e. Thats 500cm divided by 25.



Careful, the question can change. There is nothing to say they could use 75cm of bleach and dilute it to 800cm or similar. The dilution faction dones't have to be, but normally is, a whole number.

they use 25cm^3 every year...not gonna change mate.

ironclaw

celtic723 wrote: »

they use 25cm^3 every year...not gonna change mate.

It can, so never assume. :pac:

aine-maire

ironclaw wrote: »

It can, so never assume. :pac:

I think that we've all seen that assuming is BAD...(with Irish paper 2 in any case )

CallMeDoctor

Cud u help me

plz

? In the bleach titration why cant u use hydrochloric acid?
Wat is the purpose of the sulfuric acid?
Tanks !

CallMeDoctor

Cud u help me? In the bleach titration why cant u use hydrochloric acid?
Wat is the purpose of the sulfuric acid?
Tanks !

Don't use HCl as KMnO_4 oxidises the Cl- ions to Cl_2, thus affecting the titration.

You've to use H_2SO_4 to provide the H+ ions, which are necessary for the reaction to take place. If there aren't enough H+ ions present, an intermediate stage of Mn(IV) is formed, which ruins the reaction. Providing enough H+ ions ensures that the Mn(VII) is fully reduced to Mn(II)

aine-maire

CallMeDoctor wrote: »

Cud u help me

plz

?

What did you need a spoiler for?

monkseyz

what is the purpose of the potassium iodide?

aine-maire

monkseyz wrote: »

what is the purpose of the potassium iodide?

Ok that's been asked in like every single chemistry thread. Several times. :rolleyes:


It's because a solution of iodine in potassium iodide is chemically the same as a solution of iodine. ie. I3 acts the same as I2

We can't use iodine on its own, because it's not soluble in water and it vaporises at room temperature...

God, I actually hope that's right!

JSK 252

Basically the pottasium iodide is added as iodine is soluble in KI but not in water. The potassium iodide is kept in excess so that the full amount of the sodium hpyochlorite ions in the bleach react with the sodium thiosulfate in the burette such that the concentration of the ions can be determined.

THE POTTASIUM IODIDE IS IN EXCESS.

CallMeDoctor

confusing

Fringe

CallMeDoctor wrote: »

these answers arent right because u dont use any iodine in the bleach experiment !!!!
gettin confused with the thiosulfate titration!

Hahahaha.

(revise that experiment, it's probably coming up)