Qualification > Sciences
IGCSE CHEMISTRY DOUBTS
8T:
--- Quote from: Ivo on June 04, 2010, 06:49:01 pm ---What, so you don't get why it's Fe(OH)2?
--- End quote ---
no i know that its a formula NOT B1 B2 IVO PLEASE WHY DOES IT HAVE TO REACH 8 I MEAN I REAched 7 but i dnt get whats the reason behind that???
Ivo:
--- Quote from: 8T on June 04, 2010, 06:52:04 pm ---no i know that its a formula NOT B1 B2 IVO PLEASE WHY DOES IT HAVE TO REACH 8 I MEAN I REAched 7 but i dnt get whats the reason behind that???
--- End quote ---
Just making sure, you're talking about sketching the graph and why the graph reaches 8cm3 maximum height?
8T:
--- Quote from: Ivo on June 04, 2010, 06:53:35 pm ---Just making sure, you're talking about sketching the graph and why the graph reaches 8cm3 maximum height?
--- End quote ---
YES, WHY?:)
Vin:
Elaboration::
1) First reaction, FeCl3 + 3 NaOH ---> 3NaCl + Fe(OH)3
so the molar ratio is 1:3 <deduce this ratio by 1)
Second reaction, FeCl2 + 2 NaOH ---> 2NaCl + Fe(OH)2
molar ratio 1:2
so 4 cm3 of FeCl2 reacted fully with 8 cm3 of NaOH
Ivo pls. check!
Ivo:
--- Quote from: 8T on June 04, 2010, 06:55:07 pm ---YES, WHY?:)
--- End quote ---
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! :)
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