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Chemistry Doubts: Paper 1 & 2

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Firstly, hydrogen is a reducing agent and can reduce compounds of metals less reactive than it.
question says another substance (liquid) was formed after passing H2... means that sth reacted with the powdered solid.
as H2 was passed, the solid must be reduced to produce another product...the solid must be CuO (less reactive than H)
hope it helps:)
 
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Do we need to remember the colours of some compounds like FeSO4, CuO, BaSO4 etc.?
not really memorize, but u can guess them like most metal oxides are dark in colour (CuO Fe2O3), FeSO4 should be green as the test for Fe2+ is green ppt,
u should know the tests for ions and the colours can be predicted from those (BaSO4 is white solid /test for SO4 radicals, Fe2SO4 is red-brown, NaCl is white/Cl- test)
 
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in displacement reactions for halogen, is there always a colour change? if yes, it means that we have to memorize all the colours of hologens?:oops:
 
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do u know the colours changes?...can u post the important ones pls?:)
In displacement reactions for halogens, the colour change to the colour of more reactive halogen.

Flourine is a pale yellow gas at rtp
Chlorine is a greenish gas at rtp
Bromine is a reddish liquid at rtp
Iodine is black solid at rtp
Astantine is a shiny black solid at rtp

Example: 2KBr + Cl2 = 2KCl + Br2(aq) .... solution turns red
2KI + Br2 = 2KBr + I2(aq) .... solution turns *brown*
*** iodine forms brown solution in water and purple vapour when heated .
hope it helps:)
 
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9
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In displacement reactions for halogens, the colour change to the colour of more reactive halogen.

Flourine is a pale yellow gas at rtp
Chlorine is a greenish gas at rtp
Bromine is a reddish liquid at rtp
Iodine is black solid at rtp
Astantine is a shiny black solid at rtp

Example: 2KBr + Cl2 = 2KCl + Br2(aq) .... solution turns red
2KI + Br2 = 2KBr + I2(aq) .... solution turns *brown*
*** iodine forms brown solution in water and purple vapour when heated .
hope it helps:)
thanks:D surely this helps.
 
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do we need to learn the tests for Ba2+ Ca2+ Pb2+ and I- Br- ions...these are not seen often in past papers?
 
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212
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103
do we need to learn the tests for Ba2+ Ca2+ Pb2+ and I- Br- ions...these are not seen often in past papers?
For cations, learn the tests for iron (both oxidation state), copper(II), aluminium (which is the same as Pb), Zinc, calcium and ammonium ions
anions: chloride, iodide, bromide, nitrate, sulphate and carbonates.:)
 
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well i was facing the same problem few weeks ago but someone suggested me PACANS. i don't know its a good institute or not for other subjects but for chemistry there's a Female teacher. Her way of teaching is quiet good and i am happy to say that i am now 80% prepared for chemistry paper.
 
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please suggest me a good chemistry teacher :confused:........I am gonna fail it really bad
well i was facing the same problem few weeks ago but someone suggested me PACANS. i don't know its a good institute or not for other subjects but for chemistry there's a Female teacher. Her way of teaching is quiet good and i am happy to say that i am now 80% prepared for chemistry paper.
well....for o level chemistry, our coursebooks are sufficient...besides, to me, this is the easiest science sub...
but if are having problems, u can try out red spot's chemistry key points and topical papers.
the teacher of my school are brilliant in chemistry, though they are not effective for physics...sorry i cant suggest any tutor cause i am from bangladesh
but if u have any queries with any topics u can ask here...i shall try my best:)
 
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In displacement reactions for halogens, the colour change to the colour of more reactive halogen.

Flourine is a pale yellow gas at rtp
Chlorine is a greenish gas at rtp
Bromine is a reddish liquid at rtp
Iodine is black solid at rtp
Astantine is a shiny black solid at rtp

Example: 2KBr + Cl2 = 2KCl + Br2(aq) .... solution turns red
2KI + Br2 = 2KBr + I2(aq) .... solution turns *brown*
*** iodine forms brown solution in water and purple vapour when heated .
hope it helps:)
good job! thanks:D
 
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help please:
(a) why ozone is important in terms of human health? [2]
(b) write the reaction for the conversion ozone to oxygen by CFC?
 
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