CIE IGCSE Chemistry Alternative to Practical

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Our chemistry teacher thinks it was the crucible experiment. You were supposed to open and close the lid periodically since it's a vigorous reaction but make sure the smoke doesn't escape.

Does anyone know the appearance of aq. chromium chloride? lol.

the rest of the paper was pretty easy but what effect does increasing the temperature have on the results of titration? i wrote no effect, anyone else?

I'm not sure for the crucible however, it would appear to be a problem, I talked about having the calcium in a test tube, bunging the test tube, connected it to another test tube which was inside a beaker of ice, I would then measure the change in mass of the beaker as the calcium oxide condensed, idk.

The temperature increase would've caused some of the solution to evaporate off meaning there was less than 25cm^3 at the start of the experiment.

Reply 21

msmeme

Original post by examhater44

Its green

how is it green? chromium forms a green precipitate in NaOH and ammonia, but how do we know about it in solution form?

Reply 22

ladamslad3000

What was the answer to the affect on the titration reaction if you heated the alkali

Reply 23

examhater44

Original post by ladamslad3000

What was the answer to the affect on the titration reaction if you heated the alkali

No effect

Reply 24

CIEEXAMSHWE

Original post by ladamslad3000

What was the answer to the affect on the titration reaction if you heated the alkali

The temperature increase would've caused some of the solution to evaporate off meaning there was less than 25cm^3 at the start of the experiment.

Reply 25

examhater44

Original post by CIEEXAMSHWE

The temperature increase would've caused some of the solution to evaporate off meaning there was less than 25cm^3 at the start of the experiment.

Increasing temp may increase kinetic energy of particles but it doesnt have any effect on concentration. Therefore the same amount of HCL will be required!

Reply 26

CIEEXAMSHWE

Original post by examhater44

Increasing temp may increase kinetic energy of particles but it doesnt have any effect on concentration. Therefore the same amount of HCL will be required!

Didn't say it would, I said the volume would be less of sodium carbonate, it asked the effect on sodium carbonate.

Reply 27

DJShaji

Oh :/ I wrote that the reaction would occur quicker; the rate of reaction would increase. Reason being that since the particles have more kinetic energy (thanks to heating), collisions occur more frequently. The particles also now have more enough activation energy.

I thought it was a trick question, making people think that you'd need less of the acid or something idk :/

Reply 28

DhillonDodhia

Original post by msmeme

how is it green? chromium forms a green precipitate in NaOH and ammonia, but how do we know about it in solution form?

Well it is a transition metal therefore has to be coloured, and green is the obvious choice due to its precipitate.

Reply 29

examhater44

Original post by CIEEXAMSHWE

Didn't say it would, I said the volume would be less of sodium carbonate, it asked the effect on sodium carbonate.

Actually it asked for the effect on the results..........

Reply 30

CIEEXAMSHWE

Question, if you write the wrong method for the last question, but include some of the right points, will you get any marks?

Reply 31

c0mmodity

I wasn't taught the Chromium tests, so I just put white precipitate xD

Reply 32

lidzxxx

For the last one I used a condenser to cool the calcium oxide smoke to a liquid and then measured the mass of the calcium oxide liquid and solid and then removed the 2g of the calcium that was started with. No idea if I got any marks for that but was all that I could think of xx

Reply 33

examhater44

Original post by lidzxxx

I think thats a reasonable method, however the most appropriate was to use a gas syringe!

Reply 34

lidzxxx

Original post by examhater44

I think thats a reasonable method, however the most appropriate was to use a gas syringe!

Thanks ! I hope that i get a few marks for it ! What i dont understand is using the gas syringe how to you work out the MASS of oxygen that is needed? Because you cant weigh smoke? Im sure theres a reasonable way around it but i couldnt think of it in the exam so i didnt use the gas syringe experiment.xx