Qualification > Sciences
ALL CIE CHEMISTRY DOUBTS HERE !!
$!$RatJumper$!$:
Thank you for the info buddy :)
One more thing, it says "describe the reactions of the oxides with water". Again, is it fine if we just state if the oxides will be soluble or insoluble in water... or would we have to elaborate more?
Arthur Bon Zavi:
--- Quote from: $!$RatJumper$!$ on September 26, 2010, 11:50:30 am ---Thank you for the info buddy :)
One more thing, it says "describe the reactions of the oxides with water". Again, is it fine if we just state if the oxides will be soluble or insoluble in water... or would we have to elaborate more?
--- End quote ---
describe means, u have to elaborate! :D
moon:
can anyone pls explain Q2 (b), Q4 (b)(iii), (iv) & Q7 (b)Nov.2008 ppr4? thanx in advance. ???
Deadly_king:
--- Quote from: $!$RatJumper$!$ on September 26, 2010, 11:50:30 am ---Thank you for the info buddy :)
One more thing, it says "describe the reactions of the oxides with water". Again, is it fine if we just state if the oxides will be soluble or insoluble in water... or would we have to elaborate more?
--- End quote ---
Mention not :)
Hmm........sometimes it may be just enough depending on the number of marks and the trend the specific question is leading to. But truthfully, I don't think you can risk losing marks here. So to be on the safe side, mention all that you know about these reactions, relative to the question though.
Like I said earlier, the conditions are not that difficult. It won't take you much time to remember all of them. Trust me! :)
Deadly_king:
--- Quote from: moon on September 26, 2010, 08:45:50 pm ---can anyone pls explain Q2 (b), Q4 (b)(iii), (iv) & Q7 (b)Nov.2008 ppr4? thanx in advance. ???
--- End quote ---
Nov 08 P4
2.(b) Given rate= k[H2O2]a[I-]b[H+]c
a represents the order of reaction with respect to [H2O2.
b represents the order of reaction with respect to [I-].
c represents the order of reaction with respect to [H+].
NOTE : 1. The slowest step is the rate determining step.
2. The number of moles of a reactant in the rate determining step gives the order with respect to that of the reactant.
When step 1 is slowest overall : a=1, b=1 and c=0
This is because in step 1, the number of moles of H2O2 is 1 and so is I-. However H+ is not present in this equation which means it has order zero.(Reaction is independent of H+)
When step 2 is slowest overall: a=1, b=1 and c=1
IO- is formed from H2O2 and I-. Replace the first equation in the second and you'll get :
H2O2 + I- + H+ ---> HOI + H2O
From this equation note the number of moles of the respective reactants.
When step 3 is slowest overall : a=1, b=2 and c=2.
Replace the new equation found above in this third step and you'll get :
H2O2 + 2I- + 2H+ ---> I2 + 2H2O
From this equation note the number of moles of the respective reactants.
3.(b)(iii). Malachite contains copper. Copper burns to form a black solid CuO.(Copper(II) Oxide)
Form an equation for the combustion of malachite which will form carbon dioxide, steam and CuO in absence of oxygen.
Cu2O5CH2 ---> CO2 + H2O + 2CuO
Mr of Cu2O5CH2 = 221
Mr of CuO : 79.5
From equation :
1 mole of malachite produces 2 moles of CuO
221g of malachite produces 2(79.5)g of CuO.
Hence 10g of malachite will produce (2*79.5)/221 * 10 = 7.19g of CuO.
(iv)
E is copper since Iron will displace copper from copper sulfate to form iron sulfate.
CuSO4 + Fe ----> FeSO4 + Cu
Data booklet is used to see if reaction will occur by finding the electrode potential value of the cell.
Electrode potential value : +0.44 + 0.34 = +0.78V
Since the value is positive, the reaction will take place.
I sincerely hope my explanations are clear enough for you to understand. :)
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