Chemistry paper question help (AS 2017 paper 1) Watch

Bertybassett
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Hi, I have a few questions in regards to this paper and was wondering if someone could please help? For 3.3, why is it that using more concentrated acid results in a lower percentage uncertainty? I get that it results in a larger volume of acid being required, but why does this reduce the uncertainty of the burette?

For 5.2, in regards to the temperature decrease by 5 degrees, surely 5 degrees = 273+5=278 kelvin, and 300-278=22, yet the ms says the new temp is 295 kelvin? I dont get this at all?

For 6.4, how do you work this out? I dont understand how you find the ratios/proportions? thanks

https://filestore.aqa.org.uk/sample-...1-QP-JUN16.PDF
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BRADFORDmaster69
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The answer is 295K as the temp decreases by 5c from 300k
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Bertybassett
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yeah thanks I kind of know that from the ms, im just wondering why my method was wrong. also, do you know how to do the other qs
(Original post by BRADFORDmaster69)
The answer is 295K as the temp decreases by 5c from 300k
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NamesAreGay
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for 6.4 You could put 79Br and 81Br in a table 79 81

79
81
and add them
79+79 = 158
79+81 = 160
81+79 = 160
81+81 = 162
this makes up 100%
160 comes up x2 so its 50% abundance
158 and 162 comes up once so its 25% abundance


(Original post by Bertybassett)
Hi, I have a few questions in regards to this paper and was wondering if someone could please help? For 3.3, why is it that using more concentrated acid results in a lower percentage uncertainty? I get that it results in a larger volume of acid being required, but why does this reduce the uncertainty of the burette?

For 5.2, in regards to the temperature decrease by 5 degrees, surely 5 degrees = 273+5=278 kelvin, and 300-278=22, yet the ms says the new temp is 295 kelvin? I dont get this at all?

For 6.4, how do you work this out? I dont understand how you find the ratios/proportions? thanks

https://filestore.aqa.org.uk/sample-...1-QP-JUN16.PDF
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Bertybassett
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thanks a lot. if the question said there were two isotopes of Br (79Br and 81Br) in an abundance of say 1:3 respectively, would there be peaks at 160 and 162 each at 50 percent? thanks
(Original post by NamesAreGay)
for 6.4 You could put 79Br and 81Br in a table 79 81

79
81
and add them
79+79 = 158
79+81 = 160
81+79 = 160
81+81 = 162
this makes up 100%
160 comes up x2 so its 50% abundance
158 and 162 comes up once so its 25% abundance
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