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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 354705 times)

Offline DEGO

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1110 on: May 17, 2010, 04:11:44 pm »
Quote from: Lariemeeva on May 17, 2010, 03:58:17 pm
^I would have asked if there is an online ver. but it seems too good to be free, although I would have bought it or something, it's probably no use while my exam is tomorrow...Thanks anyways.

Also, can you list down all the solubles and insoluble again? This time a full list after all the corrections...

Another question, if hydrated means that it contains water then it is the same as when we say that a salt is in aqueous form right? Which means it's soluble.

So if this is right then Hydrated = Soluble/Aqueous form?

yes hydrated mean it is souble,and aqueous or crystalls
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1111 on: May 17, 2010, 04:12:03 pm »
Quote from: Nidzzz on May 17, 2010, 03:59:59 pm
hey can any1 help me hw do we noe a substance is good dehydrating agent or hydrating agent hw can we prove it  n can any1 list dem down  :)

Never heard of anything called hydrating agent. Dehydrating agent removes water of crystallisation from a hydrated salt.

Eg : Sulfuric acid removes water of crystallisation from hydrated copper(II) sulfate

Also, Phosphorus pentoxide, obtained from the decomposition of aluminium phosphate is a dehydrating agent .
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1112 on: May 17, 2010, 04:14:20 pm »
Quote from: Lariemeeva on May 17, 2010, 03:58:17 pm
^I would have asked if there is an online ver. but it seems too good to be free, although I would have bought it or something, it's probably no use while my exam is tomorrow...Thanks anyways.

Also, can you list down all the solubles and insoluble again? This time a full list after all the corrections...

Another question, if hydrated means that it contains water then it is the same as when we say that a salt is in aqueous form right? Which means it's soluble.

So if this is right then Hydrated = Soluble/Aqueous form?


First, Hydrated salts contain "Water of Crystallization". A salt in aqueous form is when it is dissolved in water. CuSO4.5H2O is not the same as NaOH(aq)

Second, Soluble is not the same as Aqueous.

Soluble means the substance can be dissolved in any liquid solvent. Aqueous is when the solvent is water.
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Offline thenewkid™

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1113 on: May 17, 2010, 04:16:32 pm »
chem p6 2006 oct/nov q6b
Thanks
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Offline Vin

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1114 on: May 17, 2010, 04:19:24 pm »
Quote from: A@di on May 17, 2010, 04:12:03 pm
Never heard of anything called hydrating agent. Dehydrating agent removes water of crystallisation from a hydrated salt.

Eg : Sulfuric acid removes water of crystallisation from hydrated copper(II) sulfate

Also, Phosphorus pentoxide, obtained from the decomposition of aluminium phosphate is a dehydrating agent .

Drying agents


Sulfuric acid

calcium oxide

anhydrous calcium chloride

;)
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Offline thenewkid™

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1115 on: May 17, 2010, 04:21:44 pm »
Quote
Never heard of anything called hydrating agent. Dehydrating agent removes water of crystallisation from a hydrated salt.

Eg : Sulfuric acid removes water of crystallisation from hydrated copper(II) sulfate

Also, Phosphorus pentoxide, obtained from the decomposition of aluminium phosphate is a dehydrating agent .

hydration means adding water. so water is a hydrating agent
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Offline Shazizzzle

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1116 on: May 17, 2010, 04:21:58 pm »
Quote from: thenewkid™ on May 17, 2010, 04:16:32 pm
chem p6 2006 oct/nov q6b
Thanks

Umm, use chromatography. Use ETHANOL as solvent as pigments are SOLUBLE IN ETHANOL not water. Then you explain the base line, how it rises up, and shows various spots on the chromatogram. You count them to get the number of different dye solid pigments in paint.
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Offline NidZ- Hero

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1117 on: May 17, 2010, 04:22:16 pm »
Quote from: ~VIN1094~ on May 17, 2010, 04:19:24 pm
Drying agents


Sulfuric acid

calcium oxide

anhydrous calcium chloride

;)
temme an experiment to prove dat  
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1118 on: May 17, 2010, 04:23:02 pm »
Quote from: ~VIN1094~ on May 17, 2010, 04:19:24 pm
Drying agents


Sulfuric acid

calcium oxide

anhydrous calcium chloride

;)

but whats for what ..6394 said earlier but i frogot to wrte down..
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Offline Lariemeeva

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1119 on: May 17, 2010, 04:24:14 pm »
A@di Thanks for the explanations, but one thing when a salt is in aqueous for then it is soluble but not all solubles are in aqueous form (dissolve in water)?
« Last Edit: May 17, 2010, 04:26:40 pm by Lariemeeva »
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Offline mdwael

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1120 on: May 17, 2010, 04:25:24 pm »
Can someone answer this question please?

"calcium carbonate is found in egg shells. All carbonates react with HCL to form chlorides. Calcium carbonate is insoluble in water but calcium chloride is soluble. Most impurities in egg shells are insoluble. Plan an experiment to find out if egg shells are 100% calcium carbonate"

This is the last question in Nov 2000 paper 6 and it is worth 6 marks.
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1121 on: May 17, 2010, 04:27:07 pm »
Quote from: thenewkid™ on May 17, 2010, 04:16:32 pm
chem p6 2006 oct/nov q6b
Thanks

Dissolve the solid in an organic solvent. Add a drop of it to the chromatogram. Commence Chromatography with a solvent.

The no. spots created on the chromatogram are the no. of colored substances

@Lariemeeva = Few substances cannot be dissolved by water, meaning they dont exist in the aqueous form. Doesn't mean they are insoluble, they can be dissolved in other organic solvents. For example : The solid from the question i answered above.

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Offline **1194**

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1122 on: May 17, 2010, 04:28:46 pm »
Can someone please tell me what a vacuum pump does ?
I don't really get it and my exam's tomorrow so I'm kinda freaked out  ..
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Offline thenewkid™

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1123 on: May 17, 2010, 04:30:32 pm »
Quote from: D@LYY on May 17, 2010, 04:28:46 pm
Can someone please tell me what a vacuum pump does ?
I don't really get it and my exam's tomorrow so I'm kinda freaked out  ..
it can create a vacuum in any closed container
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Offline Deniz

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1124 on: May 17, 2010, 04:31:31 pm »
can some1 explain how we can make indicator from berries.
i really need..
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