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Author Topic: CHEM AND BIO HELP AND TIPS HERE  (Read 333081 times)

Offline mdwael

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1125 on: May 17, 2010, 04:32:36 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 sucks all the air in making the container a vacuum (just like on the moon)
Vacuum is an empty is space with no air molecules
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Offline Shazizzzle

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1126 on: May 17, 2010, 04:33:11 pm »
Quote from: mdwael 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.

Take a sample of an egg shell, in a beaker or conical flask preferably. Add to it, excess dilute HCl, and warm to speed up the reaction. Allow calcium carbonate to react with HCl. All the calcium carbonate will produce calcium chloride and CO2 Which will evolve. Add the mixture to water. The calcium chloride will dissolve. Impurities are insoluble. Filter the mixture. If there is a residue, it is an impurity, as is insoluble, proving that the shell is NOT 100% Calcium Carbonate.
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Offline Lariemeeva

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1127 on: May 17, 2010, 04:33:19 pm »
Thanks again A@di

Anyways, I have studied until now:

1. Experimental Techniques
2. Stoichiometry
3. Electricity and Chemistry
4. Chemical Changes
5. Chemical Reactions
6. Acids, Bases and Salts

Are there any other topics I should study for tomorrow (Paper 6), and is there any topic from those that I don't need to focus on much while I'm doing my revision now?
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Offline thenewkid™

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1128 on: May 17, 2010, 04:35:44 pm »
are there any chances of electrolysis coming in 2morrows ppr?
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Offline Deniz

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1129 on: May 17, 2010, 04:37:31 pm »
can u pls explain me how we can make indicator from berries.?
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Offline Lariemeeva

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1130 on: May 17, 2010, 04:39:52 pm »
^^Yes, huge chances...
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1131 on: May 17, 2010, 04:40:25 pm »
Quote from: mdwael 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.

Take an egg shell and weigh it. Mass of egg shell = Xg

React the egg shell with HCl = Will produce Calcium chloride and CO2.

Filter. Residue = Insoluble impurities and CaCO3

Weigh the Calcium Chloride. Mass of calcium chloride = Yg

Mass of CaCO3 + Impurities = Zg

CaCO3 (100g) --> CaCl2 (111g) + CO2 + H2O

111g of CaCl2 --> 100 grams of CaCO3

Yg of CaCl2    ---> W grams of CaCO3.

% of CaCO3 in egg shels = W grams/Z grams * 100.

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Offline thenewkid™

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1132 on: May 17, 2010, 04:41:55 pm »
Quote from: Deniz on May 17, 2010, 04:37:31 pm
can u pls explain me how we can make indicator from berries.?

i dont think they'll ask u 2 how to make an indicator
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Offline Ghost Of Highbury

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1133 on: May 17, 2010, 04:42:57 pm »
Quote from: Deniz on May 17, 2010, 04:37:31 pm
can u pls explain me how we can make indicator from berries.?


Crush the berries. Mix them with water and warm the mixture. Stir. Filter.

Try the indicator on acid/base and check if it showing different colors.
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Offline Deniz

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1134 on: May 17, 2010, 04:45:50 pm »
Quote from: A@di on May 17, 2010, 04:42:57 pm
Crush the berries. Mix them with water and warm the mixture. Stir. Filter.

Try the indicator on acid/base and check if it showing different colors.

thank u so much. :)
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Offline Lariemeeva

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1135 on: May 17, 2010, 04:49:14 pm »
Can anyone help with this

Quote from: Lariemeeva on May 17, 2010, 04:33:19 pm
Anyways, I have studied until now:

1. Experimental Techniques
2. Stoichiometry
3. Electricity and Chemistry
4. Chemical Changes
5. Chemical Reactions
6. Acids, Bases and Salts

Are there any other topics I should study for tomorrow (Paper 6), and is there any topic from those that I don't need to focus on much while I'm doing my revision now?

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Offline NidZ- Hero

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1136 on: May 17, 2010, 04:56:10 pm »
http://www.chemactive.com/labs/igcse_labs.html this is a link 2 most of de practical expermient might be help ful 4 p6 chem 2 moro
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Offline **1194**

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1137 on: May 17, 2010, 05:01:16 pm »
Quote from: mdwael on May 17, 2010, 04:32:36 pm
It sucks all the air in making the container a vacuum (just like on the moon)
Vacuum is an empty is space with no air molecules

Thanks :)
Good luck :D
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Offline princess12

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1138 on: May 17, 2010, 05:03:25 pm »
can any 1 explain me what is the difference between cathode and anode
                                         good luck to all
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Offline WARRIOR

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Re: CHEM AND BIO HELP AND TIPS HERE
« Reply #1139 on: May 17, 2010, 05:05:57 pm »
Quote from: princess12 on May 17, 2010, 05:03:25 pm
can any 1 explain me what is the difference between cathode and anode
                                         good luck to all
cathode is the negative eletreod which attract CATIONS WHO ARE +
anode is the  posotive elctrode which attact teh ANIONS who are -
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