OCR B F335 - Chemistry by Design - 13th June 2012

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What did people put for the question about ionic solvents made up of large cations and anions why they have low melting points?

Low charge density means lower attraction between ions

Reply 1181

14loubylou

Original post by I failed badly

On the 1 mark question where we had to draw a curly arrow on, did the arrow go from the bond to the oxygen, or should we put it from the bond and stright down to the bond between the oxygen and carbon seen as though a c=o bond was formed?

I'm pretty sure it goes to the bond between carbon and oxygen because it uses the electrons to form a double bond with carbon

Reply 1182

14loubylou

Original post by Princess Kawaii

What did people put for the question about ionic solvents made up of large cations and anions why they have low melting points?

I put it was because of their large size they cannot pack closely together so have weaker ionic bonds therefore require less energy to separate :s-smilie:

Reply 1183

14loubylou

What did anybody get for the question on the second page where you had to work out the concentration of oxygen it was only two marks so shouldn't be too hard but i could even attempt it! :s-smilie:

Reply 1184

InkyOne

Original post by I failed badly

I drew it from the O-H bond to the C-O bond - the same thing came up on a past paper, and that was what was on the mark scheme, but the scenarios weren't exactly the same, so it could be wrong...

Reply 1185

ashleighlg

Original post by 14loubylou

What did anybody get for the question on the second page where you had to work out the concentration of oxygen it was only two marks so shouldn't be too hard but i could even attempt it! :s-smilie:

O.2/24 = 8.3x10^-3 :smile:

then you had to do 0.8/24 to get the nitrogen :smile:

Reply 1186

InkyOne

Original post by 14loubylou

What did anybody get for the question on the second page where you had to work out the concentration of oxygen it was only two marks so shouldn't be too hard but i could even attempt it! :s-smilie:

I got the concentration of the N2 to be 0.033 mol/dm3, but I though that we had to show that the conc. of O2 was what it was in the question, not work it out from scratch?

Reply 1187

Freiheit

Any more grade boundary predictions for A,B and C?

Reply 1188

14loubylou

Original post by InkyOne

I got the concentration of the N2 to be 0.033 mol/dm3, but I though that we had to show that the conc. of O2 was what it was in the question, not work it out from scratch?

it probably was! i was in a rush at the end to come back to it so doubt i even read it properly :s-smilie:

i just thought they gave you the equation and the about 1 mole of every gas takes up 24 dm3 i couldn't find any extra information it was annoying because you had to use these for a later question too.. oh well! but yours sounds about right :smile:

Reply 1189

14loubylou

Original post by ashleighlg

O.2/24 = 8.3x10^-3 :smile:

then you had to do 0.8/24 to get the nitrogen :smile:

sorry if i'm being stupid but where did you get the 0.2 from? :smile:

Need paper!

Original post by Birterillo

Errrrm, what did the question actually ask you to do?

state the molecule that would be needed to make (tri phenyl methane? ok not sure if this is the name) in addition to the alcl3 catalyst
do you remember it now???
maybe your too traumatised :smile:

( i think i am)

Reply 1192

sunshinesmile10

Original post by Lilgig

Need paper!

AY AY!

Reply 1193

tristanwong

just try and make it ourselves..

ill start it off
1i) oxidation states of Nitrogen
ii) colour changes of nitrogen
iii) advantages and disadvantages of NO2

Reply 1194

georgie94

Original post by 14loubylou

sorry if i'm being stupid but where did you get the 0.2 from? :smile:

It said in the question that the ratio of nitrogen to oxygen was 1:4 therefore for every 1 mole of air, 0.2 of it is oxygen.

Reply 1195

user3456

3) Prove that oxygen concentration is ...
Work out concentration of NO2

4) Work out the Kc for the above equation
5) Using the above information work out the concentration of (cant rememeber..)?
6) What effect does increasing the temperature have on the equilibrium constant
7) What effect does high pressure have on the equilibrium constant

sorry if i've got any wrong bt that seems to be how i remember it!

Reply 1196

user3456

Marks for the above - Q3) 2 marks, 4) 1 mark 5) 3 marks 6) 3 marks 7) 2 marks

Reply 1197

14loubylou

Original post by georgie94

It said in the question that the ratio of nitrogen to oxygen was 1:4 therefore for every 1 mole of air, 0.2 of it is oxygen.

ahh yes thanks :smile:

Reply 1198

Princess Kawaii

Oh just remembered one question it was about turning the aldehyde into carboxylic acid and it asked why this test will not distinguish between the two. What did u guys write for that?

Reply 1199

InkyOne

Original post by Princess Kawaii

Oh just remembered one question it was about turning the aldehyde into carboxylic acid and it asked why this test will not distinguish between the two. What did u guys write for that?

the other one also had a hydroxyl group that could be oxidised into a ketone (it was a secondary alcohol) which would also produce the same colour change