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ocr chemistry b salters f331 23rd May 2014 thread

bobo19966

anyhing need to notice for this I got this exam tmr arggghhh

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Reply 1

diba786

Original post by bobo19966

anyhing need to notice for this I got this exam tmr arggghhh

sameeee
Make sure u know heterogeneous catalyst
Absorption emsission spectra
Mass spectrometer
Bond angles
As they come up every time
Papers are quite repetitive tbh
GOOD LUCK

Reply 2

bobo19966

Original post by diba786

sameeee
Make sure u know heterogeneous catalyst
Absorption emsission spectra
Mass spectrometer
Bond angles
As they come up every time
Papers are quite repetitive tbh
GOOD LUCK

thanks

seems very few people to do chemistry ocr salters b????

Reply 3

ThatWasHard!

Any other predictions on what topics come up?

Heterogeneous catalysts always com tbh, as d bond angles

An tips for tonight?

Reply 4

josqu

I'm doing it :smile:

Auto-ignition and pollution always seem to come up as well.

Reply 5

pinkgorilla

Im sitting this exam too.

Piece of piss

Sulphur dioxide quite often comes up and asking to draw skeletal formulas, enthalpy changes and nuclear equations :smile:

Reply 8

bobo19966

Original post by abbielucy

Sulphur dioxide quite often comes up and asking to draw skeletal formulas, enthalpy changes and nuclear equations :smile:

these are fine what makes me scared is some of the calculation question because I can't understand the question :frown:

Reply 9

abbielucy

Original post by bobo19966

these are fine what makes me scared is some of the calculation question because I can't understand the question :frown:

Yeah me too the ones with volume of gas I just did confused me but I think I understand it now. You always just have to be really logical and write down everything you know and then decide on what triangle to use

Reply 10

Turtlefushsia

Original post by abbielucy

Sulphur dioxide quite often comes up and asking to draw skeletal formulas, enthalpy changes and nuclear equations :smile:

When you say sulphur dioxide do you mean drawing its dot cross diagram? :cool:

Reply 11

bobo19966

Original post by Turtlefushsia

When you say sulphur dioxide do you mean drawing its dot cross diagram? :cool:

Including describe the shape and bond angles maybe?

Reply 12

abbielucy

Original post by Turtlefushsia

When you say sulphur dioxide do you mean drawing its dot cross diagram? :cool:

I meant polluting gases the fact it leads to acid rain and stuff but it could ask you to draw it as well :smile:

Reply 13

Turtlefushsia

Original post by abbielucy

I meant polluting gases the fact it leads to acid rain and stuff but it could ask you to draw it as well :smile:

Oh right thanks! ..... If they did ask you to draw it and name the shape would it have 2 lone pairs and 2 bonding pairs so would it be tetrahedral with 109 angles?

Reply 14

abbielucy

Original post by Turtlefushsia

Oh right thanks! ..... If they did ask you to draw it and name the shape would it have 2 lone pairs and 2 bonding pairs so would it be tetrahedral with 109 angles?

I think it's actually trigonal planar 120 but correct me if I'm wrong it's group 6 and forms double bonds with the oxygen meaning it only has one lone pair

Reply 15

ThatWasHard!

Original post by abbielucy

I think it's actually trigonal planar 120 but correct me if I'm wrong it's group 6 and forms double bonds with the oxygen meaning it only has one lone pair

Its bent

basically:

2 bonding pairs
1 lone pair

therefore, 118 degree bond angle

which means a bent shape

Generally the rule is for every lone pair take 2 degrees off

EDIT: made a mistake :biggrin:

Lone pairs aren't counted in the shape, so its bent (or v-shaped)

(edited 9 years ago)

Reply 16

Turtlefushsia

Original post by ThatWasHard!

Yeah it is trigonal planar

basically:

2 bonding pairs
1 lone pair

therefore, 118 degree bond angle

which means a trigonal planar shape

Generally the rule is for every lone pair take 2 degrees off

Thanks for the explanation. Just wondering how do you know it's a double bond?

Reply 17

abbielucy

Original post by ThatWasHard!

Yeah that's what I thought the exam board don't care about taking degrees off with lone pairs my teacher said :smile:

Reply 18

ThatWasHard!

Original post by Turtlefushsia

Thanks for the explanation. Just wondering how do you know it's a double bond?

Original post by Turtlefushsia

Thanks for the explanation. Just wondering how do you know it's a double bond?

Ok so,

the oxidation state of oxygen is always +2

This means that oxygen always needs two electrons

So as its dioxide, it needs four electrons

Sulphur has 6 valence electrons

So two double bonds are formed, with one lone pair left

This makes it V-Shaped or bent