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    (Original post by msmeme)
    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.
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    (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?
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    What was the answer to the affect on the titration reaction if you heated the alkali
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    (Original post by ladamslad3000)
    What was the answer to the affect on the titration reaction if you heated the alkali
    No effect
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    (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.
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    (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!
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    (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.
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    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 :/
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    (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.
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    (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..........
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    Question, if you write the wrong method for the last question, but include some of the right points, will you get any marks?
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    I wasn't taught the Chromium tests, so I just put white precipitate xD
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    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
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    (Original post by 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
    I think thats a reasonable method, however the most appropriate was to use a gas syringe!
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    (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
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    (Original post by lidzxxx)
    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
    You can find the mass of smoke'
    Then do that mass minus initial mass (2g) to find mass of oxygen that reacted/combined
 
 
 
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