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Chemistry: Post your doubts here!

knowitall10

knowitall10

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raamish said:
another thing written in the marksheme ( allow the cnadidate to select up to five anomalies which must include that furthest from the line) so whats it talking abt?
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The points that do not lie on your best fit line.. they are way off and are obviously wrong. so depending on the student's line, the anomalies can be up to 5..
 
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raamish

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hey in that file i dont understand m4 and m5. Like in the experiments they ask for all of these things except these 2 that i have seen. So m4 and m5 do we have to write them in every experiment whether they ask or not. Cause i did not used to write the procedure in full detail of the experiment. In m4 about the arrangement of the apparatus is it referring to the drawing of the apparatus that we do in previous parts?? And i dont get what do we have to write in m5 at all. Can u help plzz as u have been doing all this time
 
knowitall10

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raamish said:
hey in that file i dont understand m4 and m5. Like in the experiments they ask for all of these things except these 2 that i have seen. So m4 and m5 do we have to write them in every experiment whether they ask or not. Cause i did not used to write the procedure in full detail of the experiment. In m4 about the arrangement of the apparatus is it referring to the drawing of the apparatus that we do in previous parts?? And i dont get what do we have to write in m5 at all. Can u help plzz as u have been doing all this time
Click to expand...
M4 is talking about keeping everything constant except the independant variable (which differs depending on the experiment). so for example, you keep the temp of the surroundings constant so the increased or decreased temp doesnt affect the rate of the reaction.
M5 is talking about all the steps you'll include in your experiment. this is usually given in the question. This step only applies if the plan wasn't given to you.
 
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raamish

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right thanku i get it. m5 only applies if the plan isnt given to us like in questions of marks 7 and 8. Then we can try writing this step otherwise we should not write it, is that what u r saying? and i got another question that in some apparatus when boiling the apparatus we have to keep lid on the apparatus to prevent heat loss and sometimes we dont have to put the lid on like in j11/52. can u plzz explain me why we put the lid on in some cases and not in others? thanku :)
 
knowitall10

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pearl angel said:
thanx,i've understood all the other things but could u plz tell me how to keep the other variables constant in that question?
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For example, you're going to find the rate of the reaction and you're seeing the effect of conc, so you keep the temp of the surroundings constant by using an electrically controlled thermostat or u keep the temp of the solutions constant using a thermometer...
 
knowitall10

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raamish said:
right thanku i get it. m5 only applies if the plan isnt given to us like in questions of marks 7 and 8. Then we can try writing this step otherwise we should not write it, is that what u r saying? and i got another question that in some apparatus when boiling the apparatus we have to keep lid on the apparatus to prevent heat loss and sometimes we dont have to put the lid on like in j11/52. can u plzz explain me why we put the lid on in some cases and not in others? thanku :)
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You place the lid on top of a plystyrene cup usually in experiments that involve enthalpy changes... otherwise you can pretty much get the hint from the question. like if you're heating a solid, then you have to use a test tube with a rubber bung and a connected peice of apparatus such as a gas syringe.

again, it depends on the question.. maybe someone else in the forum has a better idea...but i hope i helped you:)
 
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sagystu

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i need help on this ASAP , what happens if some one takes the formula sheet by mistake after the exam ?!
 
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xhizors

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knowitall10 said:
For example, you're going to find the rate of the reaction and you're seeing the effect of conc, so you keep the temp of the surroundings constant by using an electrically controlled thermostat or u keep the temp of the solutions constant using a thermometer**...
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Or do experiment in a thermostatically controlled room
or keep the temp of the solutions constant using thermostatically controlled water bath**!
 
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raamish

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in j11 52 c we are trying to find the rate of rxn but we are not keeping the lid on the beaker. i dont understand that to take out rate of rxn accurately shouldnt we try to reduce heat loss by putting lid?
papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_52.pdf
 
knowitall10

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raamish said:
in j11 52 c we are trying to find the rate of rxn but we are not keeping the lid on the beaker. i dont understand that to take out rate of rxn accurately shouldnt we try to reduce heat loss by putting lid?
papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_52.pdf
Click to expand...
Both, the marking scheme and the examiner's report say that no mark if sealed. So i u shouldnt place the lid. another point i noticed is tht the examiner's report said the the student confused the exp with standard enthalpy so that means that u only prevent heat loss in the enthalpy change questions.
 
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raamish

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in j12 51 2c) what is the reason for the anomalous pts and can u explain the equilibrating thing again
 
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