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chemistry 1c

mennakhaled

mennakhaled

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what you guys did in the sillicon question
i wrote it has strong covalent bonds between molecules and need high energy to overcome because it's giant macromolecule and silicon is metalloid which have high melting point
 
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schoolation

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The 4 marks are mark-schemed as the following:
1- It has a giant
2- Covalent structure
3- With strong covalent bonds
4- Need high energy to overcome
 
E

EJ007

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I got 1.2 tonnes too but as it was 2 moles of PbO react with 1 mole of Carbon so according to my thinking carbon would be having half the number of moles i cut my answer 1.2 tonnes and then wrote a new one will i be rewarded for the method ? and name one negative ion who's precipitate wont be formed i wrote Carbonate and yes the HCL i wrote its a strong acid and will vigorously react with the solution and nitric acid is used before adding silver nitrate solution thats because to make a solution of the salt and what was the relative formula mass of the sample of carbon ?
 
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EJ007 said:
I got 1.2 tonnes too but as it was 2 moles of PbO react with 1 mole of Carbon so according to my thinking carbon would be having half the number of moles i cut my answer 1.2 tonnes and then wrote a new one will i be rewarded for the method ? and name one negative ion who's precipitate wont be formed i wrote Carbonate and yes the HCL i wrote its a strong acid and will vigorously react with the solution and nitric acid is used before adding silver nitrate solution thats because to make a solution of the salt and what was the relative formula mass of the sample of carbon ?
Click to expand...

Well here you go, the 1.2 tonnes calculation, you'll get one mark

The precipitate question, obviously your answer is wrong as ALL carbonates are insoluble! So when you add anything to anything carbonate, you get a precipitate, in this question he meant to ask you " Get me a negative ion, which ALL its compounds are SOLUBLE" with no doubts, it's nitrate :)

The HCL question, is also wrong, as nitric acid is hell strong too.. but the strength or the concentrations of acid is not the important part because they are both diluted! The answer here is about HCL forming white precipitate of AgCl.. Let me remind you, silver nitrate is used to test for hallides, and how you can use a hydrochloric hallide to prepare for the use of the test of hallides??!!!!!!!!! It's not logical bro!

The relative formula mass of carbon wasn't that difficult, it was all about, Multiply the percentages by the mass numbers they gave you and add them together you'll get the relative formula mass! I can't specifically remember the answer I'm sorry :)

I hope I helped!
 
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EJ007

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schoolation said:
Well here you go, the 1.2 tonnes calculation, you'll get one mark

The precipitate question, obviously your answer is wrong as ALL carbonates are insoluble! So when you add anything to anything carbonate, you get a precipitate, in this question he meant to ask you " Get me a negative ion, which ALL its compounds are SOLUBLE" with no doubts, it's nitrate :)

The HCL question, is also wrong, as nitric acid is hell strong too.. but the strength or the concentrations of acid is not the important part because they are both diluted! The answer here is about HCL forming white precipitate of AgCl.. Let me remind you, silver nitrate is used to test for hallides, and how you can use a hydrochloric hallide to prepare for the use of the test of hallides??!!!!!!!!! It's not logical bro!

The relative formula mass of carbon wasn't that difficult, it was all about, Multiply the percentages by the mass numbers they gave you and add them together you'll get the relative formula mass! I can't specifically remember the answer I'm sorry :)

I hope I helped!
Click to expand...
Thanks bro :) hope I ll make it to get an A :)
 
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EJ007

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also carbonate ion is only identified when limewater is passed through it isnt it ? first we make a solution of the salt and the pass limewater to it anyway and yes green precipitate gave Fe+2 lilac colour gave potassium ion and carbon's relative formula mass was 8 point something like that yellow precipitate gave iodide ion or bromide ion ?? :S
 
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EJ007 said:
also carbonate ion is only identified when limewater is passed through it isnt it ? first we make a solution of the salt and the pass limewater to it anyway and yes green precipitate gave Fe+2 lilac colour gave potassium ion and carbon's relative formula mass was 8 point something like that yellow precipitate gave iodide ion or bromide ion ?? :S
Click to expand...

1- the carbonate question:- Not exactly, you should put HCL first so there is carbon dioxide gas produced, then test the gas by limewater which will turn milky
2-FE2+ yes
3- K+ is lilac yes
4- Iodide
 
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EJ007

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okay cool so looks like some of parts numbered 1 or 2 are not upto the mark :p btw whats the marking criteria ? if my method is correct and answer is incorrect will i be rewarded ?
 
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