Chemistry - Bleach Q

umph

There is a question on bleach in the sample papers so it is not in the marking scheme and there are no bleach questions from 2002-2009...

Why was an excess of potassium iodide necessary?

Thanks!

Lawliet

To ensure all the hypochlorite ions react

aine92

Excess to ensure there are enough H+ ions to allow it to react fully.

Lawliet

aine92 wrote: »

Excess to ensure there are enough H+ ions to allow it to react fully.

No. That's what the sulfuric acid is for. If your trying to ensure excess H+ ions it's always an acid.

leg

To liberate all the iodine from the Clo

Psychedelia

also iodine is insoluble in polar solvents so the presence of I minus from the KI is necessary to dissolve the iodine to carry out the titration.
(it forms the iodide ion which acts identically to iodine and is soluble.)

Lawliet

Psychedelia wrote: »

also iodine is insoluble in polar solvents so the presence of I minus from the KI is necessary to dissolve the iodine to carry out the titration.
(it forms the iodide ion which acts identically to iodine and is soluble.)

Careful now; that's a bit wordy and you didn't actually answer the question. That would have gotten nothing in the exam, as you have to make reference to the sodium hypochlorite.

theowen

Lawliet wrote: »

Careful now; that's a bit wordy and you didn't actually answer the question. That would have gotten nothing in the exam, as you have to make reference to the sodium hypochlorite.

Indeed! Keep it simple. I'm praying bleach comes up.

aine92

Lawliet wrote: »

No. That's what the sulfuric acid is for. If your trying to ensure excess H+ ions it's always an acid.

Right you are, read the question wrong my bad!