posted by TaeYeon .
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?
ok nevermind, i think i'm right. thanks for the help guys:)