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May/June 2012 Papers!!!

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I'm uploading MAY-JUNE-2012 Papers (s12 session - A Level + O Level + IGCSE) as they are being released. You can download them at

olevel.sf.net/papers

No Marking Schemes before Result!!!

The following papers are missing...
0500 English papers 12, 21, 22, 31, 33
0450 Business Studies papers 11, 12, 13, 22, 23
0455 Economics papers 13, 21, 22, 23, 32
Can you please upload them..??? Thanks...!
 
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Dude A level chemistry p42 is missing! Kindly upload ASAP!
A-Level ( chemistry) paper42! Thnks
 
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1123/22 and 1123/21 r also nt uploaded.can u plz upload them?? well thanx fr the others
 

NIM

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guys need help!!!
Q1_ Hydrated sodium carbonate has the formula Na2CO3.nH2O. An experiment was performed to determine n, the amount of water of crystallization. A sample of 50.00 g of hydrated sodium carbonate was dissolved in 250 cm3 of water. 20 cm3 of this solution reacted completely with 13.95cm3 of 2.00 mol/dm3 hydrochloric acid.

Na2CO3(aq)+ 2HCl (aq) _______ 2NaCl(aq) +CO2(g)+H2O(l)
a)Calculate the amount of HCl acid reacted.
b). calculate the amount of sodium carbonate in the 20.00 cm3 of the solution used in the reaction.
c). calculate the concentration of sodium carbonate in the sample.
d). Calculate the molar mass of the hydrated sodium carbonate.
e). Calculate the value of n.
 
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guys need help!!!

Q1_ Hydrated sodium carbonate has the formula Na2CO3.nH2O. An experiment was performed to determine n, the amount of water of crystallization. A sample of 50.00 g of hydrated sodium carbonate was dissolved in 250 cm3 of water. 20 cm3 of this solution reacted completely with 13.95cm3 of 2.00 mol/dm3 hydrochloric acid.
Na2CO3(aq)+ 2HCl (aq) _______ 2NaCl(aq) +CO2(g)+H2O(l)
a)Calculate the amount of HCl acid reacted.
b). calculate the amount of sodium carbonate in the 20.00 cm3 of the solution used in the reaction.
c). calculate the concentration of sodium carbonate in the sample.
d). Calculate the molar mass of the hydrated sodium carbonate.
e). Calculate the value of n.
Pls tell me the paper it is from... Mayb then I ll b able to answer this...
 
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a) 1.02g => 0.0279 moles

b) 4g => 0.01395 moles

c) 0.6975 g/dm3

d) 286.73

e) 10
Do you have the answers? These are what I got so far..hope its correct xD!
 
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