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CHEMISTRY PAPER 3 DOUBTSS!!

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Zaki ali asghar

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there was an equation given by student in q2 and we had to tell why was it wrong,did we have to prove that using Mr? Because 1 :1 ratio was giving 40g of decomposition product rather than 50 . sth
 
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sarmadimran

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Zaki ali asghar said:
there was an equation given by student in q2 and we had to tell why was it wrong,did we have to prove that using Mr? Because 1 :1 ratio was giving 40g of decomposition product rather than 50 . sth
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Ye I also proved by Mr 44 g CO2 will be produced instead of 52.3
 
techgeek

techgeek

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sarmadimran said:
Why lid is placed while cooling? And improvement?
I wrote to prevent residue loss and improvement use larger mass so that uncertainty will be reduced...
And what was your percentage purity ?mine was 99.5%
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ahh! that improvement thing really got me stuck otherwise it went well... then I wrote to titrate the product to calculate it's mass, does that sound sensible?
btw I don't think the lid was placed to prevent residue loss, a) residue was not being lost b) water was being lost but we wanted it to escape, not to stay back... so I wrote it was so product is not oxidized back to NaHCO3
I got percentage uncertainty of around 94. sth and I think it had to be that because the one given in the next part was 95. th so it had to be around that
 
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sarmadimran

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techgeek said:
ahh! that improvement thing really got me stuck otherwise it went well... then I wrote to titrate the product to calculate it's mass, does that sound sensible?
btw I don't think the lid was placed to prevent residue loss, a) residue was not being lost b) water was being lost but we wanted it to escape, not to stay back... so I wrote it was so product is not oxidized back to NaHCO3
I got percentage uncertainty of around 94. sth and I think it had to be that because the one given in the next part was 95. th so it had to be around that
Click to expand...
Yes u r correct lid was placed to prevent oxidation however regarding percentage impurity I got 99.5% and it may vary from person to person..
 
amina1300

amina1300

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how did you guys calculate the percentage purity?? Why did I get it around 10 percent??
 
techgeek

techgeek

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hadeel25081999 said:
I got around 9.5% but the people who are getting around 95% , I think they multiplied by 10 in the question where we had to find the mass
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first I got about about 9.5% too but then I realized when I came to next part that it should be around 95%, so I went back and found the mistake that I had not taken into account the 250cm3 which we had diluted instead I had used the no. of mol in 25cm3 so multiplying it by 250 and taking into account dilution factor, I got it correct
 
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hadeel25081999

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techgeek said:
first I got about about 9.5% too but then I realized when I came to next part that it should be around 95%, so I went back and found the mistake that I had not taken into account the 250cm3 which we had diluted instead I had used the no. of mol in 25cm3 so multiplying it by 250 and taking into account dilution factor, I got it correct
Click to expand...
You got a titre number of around 23.3
 
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