Qualification > Sciences
ALL CIE CHEMISTRY DOUBTS HERE !!
Deadly_king:
--- Quote from: $!$RatJumper$!$ on November 17, 2010, 06:56:28 am ---Yeah some of us arent as clever as you guys hey :)
But thankx.. no worries if you're busy...
i got how to do Q16, 25, 30, 31 and 34 .. so no need for those :)
--- End quote ---
It's not about being clever dude. You're going to have the same exams in 2 days, so you should have been ready. :)
Nov 05 p1
12. You just need to write the balanced equations for the complete combustion of one mole of each element.
Mg + 1/2O2 ----> Mg0
Al + 3/4O2 ----> 1/2Al2O3
S + 3/2O2 ----> SO3
Hence we can note that the number of moles of oxygen required increases but not constantly from Magnesium to Sulfur. ;)
Answer is D
15. You should first write the balanced equation representing the decomposition of the nitrate. That will be:
Ca(NO3)2 -----> CaO + 2NO2 + 1/2O2
From equation:
1 mole of nitrate gives 1/2 mole of oxygen gas.
164g of nitrate produces (24/2) dm3 of oxygen gas.
Hence 8.2g of nitrate will emit (12/164 x 8.2) = 0.6dm3 = 600cm3
Answer is C
19. Chiral centres are shown by a carbon atom carrying 4 different group of atoms. No carbon involved in a C=C will be able to show chirality.
Hence this leaves us with only two chiral centres. Starting from the right, they are the second and the third carbon atom
Answer is B
24. I'll proceed by elimination.
Propan-2-ol and 2-methyl-propan-2-ol are first to be rejected since they can form only one type of alkene due to free rotation. ;)
2-methylbutan-2-ol can form only 2 types of alkenes due to free rotation. It is connected to three other carbon atoms and should have been able to form 3 alkenes but two of them are identical.
Butan-2-ol should have formed only two types of alkenes but one of them show cis-trans isomerism. Hence it forms 3 types of alkenes.
Answer is A.
36. A reaction in which the same element is both oxidized and reduced is called a disproportionation reaction.
Is that enough or should I go in more details?
39.
Unburnt hydrocarbons are made to burn completely to form carbon dioxide and water. Hence this is a form of oxidation. Oxygen comes from the oxides of nitrogen which in turn gets reduced. ;)
$!$RatJumper$!$:
Thankx a ton for the help buddy! :)
I understood all that you mentioned.. but i think you did no 19 instead of no 18 :)
If you have time please do it, otherwise its fine. Thankx again +rep
Deadly_king:
--- Quote from: $!$RatJumper$!$ on November 17, 2010, 09:30:41 am ---Thankx a ton for the help buddy! :)
I understood all that you mentioned.. but i think you did no 19 instead of no 18 :)
If you have time please do it, otherwise its fine. Thankx again +rep
--- End quote ---
Anytime ;)
Ooh yeah.......I'm sorry for the confusion.
18. CaO is a basic oxide while ammonium sulfate is some kind of acidic as H+ can be liberated from NH4+. So they'll react together to give off ammonia, which being a gas will rise into the atmosphere. Hence the soil will lose its nitrogen which is required by plants.
Answer is C.
$!$RatJumper$!$:
Thank You :)
Hypernova:
+ rep DK for all of that
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