Look, the skeletal formula does not show all the bonds, only the bonding pairs. Each carbon atom has 4 outer electrons therefore will create 4 bonds. In this case it had 3 bonding pairs as shown through the lines in the skeletal formulae, but there was a lone pair that is also around the central C atom. It is tetrahedral and 109 degrees.
Don't worry I was kicking myself afterwards as well...

urgh thats 2 marks
i would have still gained marks for saying that the bond angle b is 120, because there are 3 areas of electron density and therefore electrons repel each other pushing each other far apart - the furthest apart possible is 120.

and for the absorption and spectrometer questions
does anybody know what the actual answer was?
i kind of wrote everything i knew for the absorption one.

Reply 287

Welbeck

3

for the last question i mentioned about the period would that give the mark? Surely the mark scheme will say either group number or period number?

Reply 288

King Hotpie

15

Was the last one not number of protons?

Reply 289

chriselle15

Original post by smileitsfree

Some things are best left unsaid.

You badman haha

Reply 290

chriselle15

Original post by NielsBohrsDad

urgh thats 2 marks
i would have still gained marks for saying that the bond angle b is 120, because there are 3 areas of electron density and therefore electrons repel each other pushing each other far apart - the furthest apart possible is 120.

and for the absorption and spectrometer questions
does anybody know what the actual answer was?
i kind of wrote everything i knew for the absorption one.

That's correct for the first part, the second part I think it was talking about angle b thus that's not correct. But you're right its only 2 marks, of which I've definitely lost lol

Reply 291

NielsBohrsDad

Original post by chriselle15

That's correct for the first part, the second part I think it was talking about angle b thus that's not correct. But you're right its only 2 marks, of which I've definitely lost lol

And err, what about the oxygenate one?
I wrote something like less oxygen required for the complete combustion of the fuel, therefore in petrol less oxygen would be needed to burn the petrol than is needed for the corresponding alkane.

and that co2 and so2 question was really annoying!!
I thought it was a common sense question so i simply wrote- The middle atom(silicon and carbon dioxide) is different in both!!

Reply 292

NielsBohrsDad

Original post by chriselle15

Lol I don't understand how you managed to take these pictures?

we await patiently.

Reply 293

saberahmed786

13

What was the general consensus on the paper by everyone? Hard? Easy? Do-able? Absolutely solid?

Reply 294

ruhit

I think i did okay but i think i made very silly mistakes which probably got me out of the grade a range hopefully not though . I think i dropped 11 marks

Reply 295

Izar

1

Original post by smileitsfree

2 reps next

I got everything i wanted without giving you a single reps. ^ There were people stressing out, having mini heart attacks, begging you to put it up and all you could think about was your reps?
i gave you a negative rating and tbh, i think other people should too.

Arsewipe.

Reply 296

chriselle15

Original post by NielsBohrsDad

And err, what about the oxygenate one?
I wrote something like less oxygen required for the complete combustion of the fuel, therefore in petrol less oxygen would be needed to burn the petrol than is needed for the corresponding alkane.

and that co2 and so2 question was really annoying!!
I thought it was a common sense question so i simply wrote- The middle atom(silicon and carbon dioxide) is different in both!!

Well I wrote more oxygen to aid in complete combustion, which increases in the efficiency of the fuel. I should have written about less CO and C produced thinking back, but not sure how many marks it was.

A lot of people wrote what you wrote, apparently the answer was silicon only has 2 bonding pairs with carbon because of the simple molecular structure? I stupidly wrote something about dative bonds.

Reply 297

NielsBohrsDad

Original post by chriselle15

Well I wrote more oxygen to aid in complete combustion, which increases in the efficiency of the fuel. I should have written about less CO and C produced thinking back, but not sure how many marks it was.

A lot of people wrote what you wrote, apparently the answer was silicon only has 2 bonding pairs with carbon because of the simple molecular structure? I stupidly wrote something about dative bonds.

i dont get that though carbon dioxide dot cross diagram had 2 electron pairs shared by carbon and oxygen on either side. and the question asked about the dot cross diagram. they both hav double bonds. and it didnt ask about the structure of the giant network just the dot cross...

also there was another question later about properties i remember what was that question?

Reply 298

krisshP

14

I got my real F331 exam in June. My mock eam today was this paper.

What did everyone say for the question how dot and cross diagram of silicon dioxide was different from that of carbon dioxide??

thanks

Reply 299

NielsBohrsDad

Original post by krisshP

I got my real F331 exam in June. My mock eam today was this paper.

What did everyone say for the question how dot and cross diagram of silicon dioxide was different from that of carbon dioxide??

thanks

I wrote that the carbon and silicon atoms in the molecules make them different
i really dont think it was a remembrance question
more of a common sense and make you think hard, when its really that easy question
Because it did only mention the carbon dioxide and Silicon dioxide dot and cross diagrams- not the giant covalent networks

There has actually been a couple of 1 markers theyv tended to throw in every now and then- such as one similar one for Paraffin wax in the past- Where it asked what was in the wick and all you had to say was something sensible such as hydrocarbon, or fuel

If you understand what i mean

OCR Chemistry B (Salters) Thursday 10th January Discussion

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