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doubts

Ask questions of CBSE Class X and discuss the same here. For any doubts relates to CBSE Class X.
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Re: doubts

Postby karthick » Sun Mar 23, 2008 11:59 am

KK ..NOW I UNDERSTAND i think they shd have put changed instead of increased or decreased
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Re: doubts

Postby vivek » Sun Mar 23, 2008 2:29 pm

karthick wrote:1what happens when washing soda crystal is exposed to air ?is it looses 9 water of crystalisation
2what is white light
3why does ordinary soap cause irritation
4How will you explain – the phenomena of electromagnetic induction in one – coil when current passing through a neighboring coil increase or decrease?(did not understand question)
5Name two types of drugs used in chemical method of population control?
6What is the composition of nervous system in higher vertebrates?


5th ques. -- 'oral pills' AND 'vaginal pills'
3rd ques. -- this is because the water may contain Mg and Ca salts with which the ordinary soaps dont function..it might also be bcoz of the added chemical scents in it [not sure]
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Re: doubts

Postby naman » Sun Mar 23, 2008 10:00 pm

doesnt de washing soda crystal loose 10 water molecules
because washing soda is
Na2CO3.10H20
???
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Re: doubts

Postby bcappu » Sun Mar 23, 2008 10:04 pm

naman wrote:doesnt de washing soda crystal loose 10 water molecules
because washing soda is
Na2CO3.10H20
???

Nope. It looses 9 water molecules.
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Re: doubts

Postby naman » Sun Mar 23, 2008 10:06 pm

how?
is dis reaction dere in textbook
and if it is heated it will have left Na2CO3.1H20?
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Re: doubts

Postby karthick » Sun Mar 23, 2008 10:18 pm

it looses 9 crystals .....
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Re: doubts

Postby bcappu » Sun Mar 23, 2008 10:57 pm

naman wrote:how?
is dis reaction dere in textbook
and if it is heated it will have left Na2CO3.1H20?


it looses nine crystals and leaves H20 as a product. Here is the equation

Na2CO3.10H20 on heating gives Na2CO3 + H20
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Re: doubts

Postby karthick » Sun Mar 23, 2008 11:18 pm

no it is na2co3.10h20->na2co3.h20 +9 h2o
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Re: doubts

Postby bcappu » Sun Mar 23, 2008 11:36 pm

karthick wrote:no it is na2co3.10h20->na2co3.h20 +9 h2o


ic, got a bit confused :? :? , thanks :D
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Re: doubts

Postby karthick » Sun Mar 23, 2008 11:43 pm

it has to obey the law of conservation of mass
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