Qualification > Sciences
IGCSE CHEMISTRY DOUBTS
gaurav95:
I mean 6bii
and u stii havent given ans to 4biii
gaurav95:
Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
Saladin:
--- Quote from: gaurav95 on June 05, 2010, 04:55:56 pm ---Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
--- End quote ---
4B(i) A metal like Sodium or Potassium. Because these metals are from group 1 and 2.
7(b) It would release Nitrogen Dioxide, so it would be a brown gas....
Ivo:
--- Quote from: gaurav95 on June 05, 2010, 04:53:33 pm ---I mean 6bii
and u stii havent given ans to 4biii
--- End quote ---
s04
4) b) ii):
--- Quote from: Ivo on June 04, 2010, 07:08:28 pm ---Well, as I explained before. The sodium hydroxide is in excess, so the maximum needed to fully react with the iron(III) chloride is 12cm3. So, simplify the ratio down to 12:4 = 3:1/ So 3 moles of sodium hydroxide reacted with 1 mole of iron(III) chloride. So the balanced equation is:
3NaOH + FeCl3 -> 3NaCl + Fe(OH)3
OK, now if iron (II) chloride:
2NaOH + FeCl2 -> 2NaCl + Fe(OH)2
So 2 moles instead of 3 was required. So if 3 moles was 12cm3, then 1 mole is 4cm3, then 2 moles must be 8cm3. Done! :)
--- End quote ---
4) b) iii):
--- Quote from: Ivo on June 04, 2010, 06:39:30 pm ---What specifically did you not get, I can try and elaborate.
And for iii) The graph would rise to maximum height, then decrease to zero again. Why? Well because aluminium hydroxide (the product formed) dissolves in excess. Think of the test for aluminium cation: add aqueous sodium hydroxide, soluble in excess giving a colourless solution. Same applies here, when a small volume was added, there was precipitate, as you add more and more, it goes colourless, therefore no precipitate. The common mistake is to think of reactivity.
I hope that clears the issue somewhat. :D
--- End quote ---
What don't you get for Q7) b). I thought i made it quite clear. What don't you get?
Any more?
Ivo:
--- Quote from: gaurav95 on June 05, 2010, 04:55:56 pm ---Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
--- End quote ---
w04?
4) b) i) It would increase because silver is less reactive than tin, so now the difference in reactivity between zinc and silver is greater, therefore the voltage would increase.
Next time, please state which session and year, because I think you're asking me doubts from both s04 and w04, I'm getting confused!
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