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IGCSE CHEMISTRY DOUBTS
gaurav95:
HI i have a pro
M/J 2002
q5 whole ms isnt there.....
can somebody pls tell me thx a lot...........
gaurav95:
Frnds sorry but one more q
4 c i
can somebody explain me how did one get that ans..................
Ivo:
--- Quote from: gaurav95 on June 03, 2010, 04:03:05 pm ---HI i have a pro
M/J 2002
q5 whole ms isnt there.....
can somebody pls tell me thx a lot...........
--- End quote ---
Gosh, how many times do I have to say this. Only joking, it's not you're fault for not knowing! :D
Here are the answers, not mark scheme but they are perfectly acceptable.
--- Quote from: nid404 on May 30, 2010, 09:17:51 am ---the a) part?
Liquids take the shape of the container, they maintain their volume. The intermolecular forces in liquids are significant and therefore, they do not expand to occupy all the space available (as gases do). A given mass of liquid has a fixed volume. also molecules in liquid have less k.e as compared to that of gases.Particles in gases have very weak intermolecular forces and high kinetic energy, hence the particles move independent of each other and occupy the space available to them.
--- End quote ---
--- Quote from: ~ A.F ~ on May 30, 2010, 10:39:18 am ---b)i) rate= time and volume. In other words, its the volume produced and the time taken.
ii) CO2 due to lower molecular mass. or less density
--- End quote ---
--- Quote from: Ivo on May 30, 2010, 01:00:49 pm ---The equation you need to use is:
Volume of gas (in dm3)
Moles of gas = --------------------------
24
Note to convert cm3 to dm3, divide quantity by 1000 (e.g. 20cm3/1000=0.02dm3)
This is the proper theory and equation behind my calculations below.
Here are the answers for 5) c) as requested:
i) Moles of C4H6: 0.02/24=0.000833
From equation, we know 2 moles of C4H6 reacts with 11 moles of O2
Therefore, moles of O2: 0.000833*5.5=0.00458
Therefore, volume of O2: 4.58*24*1000=110cm3
ii) From equation, we know 2 moles of C4H6 produces 8 moles of CO2
Therefore, moles of CO2: 0.000833*4=0.00333
Therefore, volume of CO2: 0.00333*24*1000=80cm3
iii) From equation, we know 2 moles of C4H6 produces 6 moles of H2O
Therefore, moles of H2O: 0.000833*3=0.0025
Therefore, volume of H2O: 0.0025*24*1000=60
Therefore, total volume of gases is simply volume of CO2 + volume of H2O:
80+60=140cm3
Alternatively, 8+6=14, so 2 moles of C4H6 produces 14 moles of products
Therefore, moles of products: 0.000833*7=0.00583
Therefore, volume of products: 0.00583*24*1000=140cm3
For part d), you use this formula:
Mass
Moles = ------
Mr
d) From the above equation, 1 mole of butyne forms 3 moles of water
Number of moles of butyne reacted: 9/54=0.167
Number of moles of water formed: 0.167*3=0.5
Mass of water formed: 0.5*(2+16)=9g
I hope this has helped. :D
--- End quote ---
Ivo:
--- Quote from: gaurav95 on June 03, 2010, 04:19:59 pm ---Frnds sorry but one more q
4 c i
can somebody explain me how did one get that ans..................
--- End quote ---
Right, the molecular formula is simply the formula showing the type and number of each element present in a molecule. So very simple, just count the number of carbon, oxygen and atoms. The answer is C6H8O6.
gaurav95:
--- Quote from: Ivo on June 03, 2010, 04:26:15 pm ---Right, the molecular formula is simply the formula showing the type and number of each element present in a molecule. So very simple, just count the number of carbon, oxygen and atoms. The answer is C6H8O6.
--- End quote ---
but there are OH groups also so i thought that it could be alcohol but its not like that right ???????????????
and also same q paper q 7 biii.......................pls
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