November 28, 2015

Homework Help: Chemistry 12

Posted by TaeYeon on Wednesday, October 6, 2010 at 12:18am.

Hello fellow comrades, I was assigned the sulphur clock reaction lab and I'm a tad bit confused by it.

Anyway, here's the lab procedure:

1. take 5 test tubes, labeled a,b,c,d and e. accurately measure out 10.0 ml of .20M sodium thiosulphate in test tube A

2. in the other test tubes measure successively 9,7,5 and 3ml of sodium thiosulphate

3. in test tubes b,c,d and e add enough water to make the total volume of solution up to 10.0ml

4. take 5 test tubes labeled a,b,c,d,e accurately measure out 10.0ml of 1.0M HCL solution in each test tube

5. mix soluations a with a , b with b etc in following way : pencil draw cross on a sheet of white paper and place empty erlenmeyer flask on this cross. pour into erlenmeyer flask, solutions A at the same time. measure the length of time that it takes for cross to dissappear

6. repeat for solutions B to E

so the The question is asking me what the variable factor is and what causes the disappearance of the "cross"

I wrote that the variable factor in the experiment is the concentration of sodium thiosulphate and the cross dissappears because of the precipitation of the sulphur.

Is that a good answer?

Please help!

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