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OCR Chemistry B (Salters) Thursday 10th January Discussion

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Bond b was 120 degrees because there were 3 bonding pairs of electrons which formed a triangular planar shape, each pair repels one another to be as far away as they can to minimise repulsion.
Bond a was 109 degrees because there were 4 bonding pairs which forms a tetrahedral shape, therefore the angle is less than b.

Question about heteregeneous and catalyst;
The definition of heterogeneous- when the catalyst is in a different phase/physical state to the reactants.
A catalyst speeds up the rate of a reaction without getting used up and lowers activation energy

Angle b is 120!

Original post by laurasales86

It's skeletal so would not show the hydrogen. I think it should be 109 because the four areas of electron density repel one another... Ect sure you will do fine :-)

oh B has a double bond so the four electrons count as one area Of electron density 120. A has four area 3x carbon and one hydrogen= 109. Hope this helps :wink:

Reply 263

Maat

past paper january 2009, question 2bii) - its 120! (angle b)

Reply 264

fattail95

Original post by smileitsfree

you know the deal.. 2 reps

We're waiting in anticipation :wink:

next post 5 reps

Btw what did you gus put for the very last question?

Reply 268

fattail95

Original post by smileitsfree

next post 5 reps

Pushing it a tad, no? Can't you just post the pages to help us out rather than use it as leverage for personal gain?

Reply 269

fattail95

Original post by Richyp22

Btw what did you gus put for the very last question?

Group number, corresponding to amount of electrons in outer shell.

Reply 270

Quiggle

Original post by Richyp22

Btw what did you gus put for the very last question?

Original post by fattail95

Group number, corresponding to amount of electrons in outer shell.

I put that too, but I also mentioned about the period the element is in and that it shows the amount of occupied electron shells.

Reply 271

smileitsfree

Original post by fattail95

Pushing it a tad, no? Can't you just post the pages to help us out rather than use it as leverage for personal gain?

do you have the paper?

i didnt think so. next post 10 reps if you keep complaining.

Reply 272

NielsBohrsDad

So, what was the answer to the oxygenate question?
I remember writing the only thing that came to my head- that it requires less oxygen to be completely burnt- therefore the petrol having an oxygenate instead of the corresponding alkane it would require oxygen

Pretty sure there was a better answer and i dont know if i would get any marks for this answer?

Reply 273

Mangodepo11

Original post by fattail95

Group number, corresponding to amount of electrons in outer shell.

Original post by Quiggle

I put that too, but I also mentioned about the period the element is in and that it shows the amount of occupied electron shells.

I wasnt sure so I put. Number of eleectrons on outer shell and number of energy levels. So i put both.

Reply 274

Mangodepo11

Nope, reduces incomplete combustion. Due to the fuel now having a higher oxygen to carbon ratio. First sentence will probably surfice though

(edited 11 years ago)

Reply 275

xOsugaplumfairy

For bond angle Q the first question bond B = 109 due to the double bond and A=120!!!!!!! 4 electron pairs = 109!!!!! 3 electron pairs = 120!!!!!
Look in your text book guys!

Reply 276

NielsBohrsDad

Original post by xOsugaplumfairy

For bond angle Q the first question bond B = 109 due to the double bond and A=120!!!!!!! 4 electron pairs = 109!!!!! 3 electron pairs = 120!!!!!
Look in your text book guys!

No!!!
One pair of electron density is still the case when there is more than one pair of bonding electrons. so even if there was a nitrogen case here- with 3 bonding pairs, it would still be one area of electron density because thats just the rule...

Reply 277

Quiggle

Original post by Richyp22

Nope, reduces incomplete combustion. Due to the fuel now having a higher oxygen to carbon ratio. First sentence will probably surfice though

Yup, I put this too :smile:

Reply 278

NielsBohrsDad

Can somebody just explain to me correctly, seeing as i can see the paper now, and show me how its 109? i just want to know where i went wrong

Reply 279

chriselle15

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...