Qualification > Sciences
Chemistry Help HERE ONLY !!
Coco:
im aiming for a 100% :) [which i wont get cuz i screwed up paper 6]
n yes 10 years is ideal
Thanx yo!
lana:
somebody please explain this to me ...when a reaction cool or lose heat it's endothermic right ? because energy is taken in ? please correct me if I'm wrong because in pp3 in June 08 mark scheme it's the opposite !!! so I'm totally confused :-\
unknown 101:
--- Quote from: emi on May 29, 2009, 03:21:57 pm ---thanks guys i get the first part all now .. but about part ii the max moles , is it like always if there is one mole it will me 0.08 ?
and why we didnt use the 10.4 in anything ??
can some one just complete that part till the percentage yield thanks <3
--- End quote ---
its because you do not know the mass of NiSO4 that reacted, maybe half of it reacted , all u know i that the number of moles of NiSO4 is 0.08 mol
and since it is 1:1 ratio so, if all the NiSO4 reacted that means that maximun number of crystals would be fromed which has a mol of 0.08 (1:1 ratio)
and to find the maximum mass use the formula: mass = moles x mr ----> 0.08 x 281 = 22.48
so that is the maxmun mass that could be produced
the percentage yeild is given by the formula : mass given/theoritical amount x 100
so in this case 10.4/22.48 x 100 = 46.3%
unknown 101:
--- Quote from: lana on May 29, 2009, 03:28:38 pm ---somebody please explain this to me ...when a reaction cool or lose heat it's endothermic right ? because energy is taken in ? please correct me if I'm wrong because in pp3 in June 08 mark scheme it's the opposite !!! so I'm totally confused :-\
--- End quote ---
hahahah ur right, but in jun08 u misunderstood it probabley, cuz over the arrow its says cool, that means that when u cool it it gives u a greater yeild of COCl2, because the forward reaction is exo so decreasing temp would shift equliberium to the right , to increase temp thus producing more yeild of COCl2
emi:
thanks alot
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