OCR F321 - 23rd May

Felt like we might as well use this procastanation on TSR to do some revision. Not seen any other thread for this exam so sorry if there is. So. Get those word perfect definitions sorted and those annoying long questions cracked :biggrin:

Easy one to begin with:
Define a covalent bond.

Reply 1

rukan

Original post by dream_merchant

Felt like we might as well use this procastanation on TSR to do some revision. Not seen any other thread for this exam so sorry if there is. So. Get those word perfect definitions sorted and those annoying long questions cracked :biggrin:

Easy one to begin with:
Define a covalent bond.

A covalent bond is a bond formed by a shared pairs of electrons.
In a covalent bond an electron pair occupies the space between the two atoms nuclei, the negatively charged electrons are attracted to the positive charges of both nuclei. this attraction overcomes the repulsion between the two positively charged nuclei, the resulting attraction is the covalent bond that holds the two atoms together.

Reply 2

pastpaper-guy

7

im retaking this exam. havent started anyy revision for this because i have unit 4 and 5 to do.

Can anyone explain the following:
First ionisation energy
shapes and bond angles
how to write ionic equations (doing A2 and still dont know this properly)

Reply 3

LimeTree.

12

Original post by pastpaper-guy

im retaking this exam. havent started anyy revision for this because i have unit 4 and 5 to do.

Can anyone explain the following:
First ionisation energy
shapes and bond angles
how to write ionic equations (doing A2 and still dont know this properly)

First Ionisation Energy is the least amount of energy required to remove one electron from a neutral atom in gaseous state.
Second Ionisation Energy is the least amount of energy to remove a second electron from an atom in gaseous state.
etc etc

Ionic equations? uhhm Mg -> Mg^2+ + 2e^-? That type of thing? sorry.. dont understand what you want to know :P
Just remember OILRIG (Oxidation is Loss, Reduction is Gain)
Meaning Oxidation is loss of electrons, Reduction is the gain of electrons.

Oxidising Agent is the same (in effect) as a reduction.. so just remember that Oxidation Agent = Reduction... Reducing Agent = Oxidation... easy peasy :P

The shape thing.. uhhm Its been a while since Ive done this.. but i'll give it a go :smile:

I'll use H20 for this example :smile:

Find out the number of electrons on the outer shell of the central atom.. in this case oxygen. In the outer shell there are 4 electrons... now add 1 electron from each hydrogen (this is adding the electron the hydrogen atom shares to form a covalent bond) so in total we have 6 electrons. Divide by two to find the total pairs of paired electrons... in this case 6/2=3.. so 3 pairs of electrons. We now need to find out how many of those pairs are bonding pairs, and how many are lone pairs.... There is 2 hydrogen atoms bonded to the oxygen, so we know that there are 2 bonding pairs.. this means by deduction there is 1 lone pair.

So from this we now know that H20 has 1 lone pair and 2 shared pairs.... With out the lone pair this shape would be linear, however due to the lone pair repulsion theory.. it is Bent (haha) or angular. As the lone pair repells the covalent bonds.

Sorry for the long explanation.. hope this helps

(edited 13 years ago)

Reply 4

dream_merchant

OP

7

Original post by pastpaper-guy

im retaking this exam. havent started anyy revision for this because i have unit 4 and 5 to do.

Can anyone explain the following:
First ionisation energy
shapes and bond angles
how to write ionic equations (doing A2 and still dont know this properly)

First Ionisation Energy-The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Bond angles.png26.3KB

tetrahedral is 109.5

OP

Original post by Tyles

tetrahedral is 109.5

Just realised i missed it off the pic, thanks :smile:

Reply 7

INeedToRevise

8

Original post by pastpaper-guy

im retaking this exam. havent started anyy revision for this because i have unit 4 and 5 to do.

Can anyone explain the following:
First ionisation energy
shapes and bond angles
how to write ionic equations (doing A2 and still dont know this properly)

I'm the same as you. Doing F324 and F325 and haven't done anything for this at all!

Reply 8

intellectual1

3

Remember F324 presumes knowledge of F321 and F322, similarly F325 presumes knowledge of AS and F324. Definitions and Calculations are very easy marks if you learn them well. Always remember that the number of marks is the number of points expected. Does anyone write in bullet point form? Or do you write the longer explanations in prose?

Reply 9

dream_merchant

OP

7

Original post by intellectual1

Remember F324 presumes knowledge of F321 and F322, similarly F325 presumes knowledge of AS and F324. Definitions and Calculations are very easy marks if you learn them well. Always remember that the number of marks is the number of points expected. Does anyone write in bullet point form? Or do you write the longer explanations in prose?

I write in bullet points as i find it easier and ive been taught the model answers in bullet points :biggrin:

Reply 10

intellectual1

3

January 2011 was quite a hard paper, so do you think we'll have an easy paper on Monday with 52/60 for A grade in June 2010 it would only just get you 72UMS?!
The topic of Shapes of molecules and ions has to be very precise or they don't award all the marks...Group 1,2 and 7 Chemstry tends to feature heavily in the exams as well

Reply 11

godknows

Original post by intellectual1

January 2011 was quite a hard paper, so do you think we'll have an easy paper on Monday with 52/60 for A grade in June 2010 it would only just get you 72UMS?!
The topic of Shapes of molecules and ions has to be very precise or they don't award all the marks...Group 1,2 and 7 Chemstry tends to feature heavily in the exams as well

I hope so :/

Reply 12

INeedToRevise

8

Original post by intellectual1

January 2011 was quite a hard paper, so do you think we'll have an easy paper on Monday with 52/60 for A grade in June 2010 it would only just get you 72UMS?!
The topic of Shapes of molecules and ions has to be very precise or they don't award all the marks...Group 1,2 and 7 Chemstry tends to feature heavily in the exams as well

Have you got the Jan 2011 markscheme??

(edited 12 years ago)

Reply 13

attysafe

HELP!!!!
Reatking F321 and doing F322!!!
Done no revision what so ever.
Can someone pass me on some notes or some kinda of help?

Reply 14

arvin_infinity

3

Anyone knows how to do Q2 a iii jan 11

!! help me out pls

Reply 15

njordan11

hi, can anyone tell me how you tell the difference/ what is the difference between pyramidal and tetrahedral?? thanks

Reply 16

301lw

Original post by njordan11

hi, can anyone tell me how you tell the difference/ what is the difference between pyramidal and tetrahedral?? thanks

both have four electron densities/pairs surrounding the central atom and but pyramidal has one lone pair of electrons

Reply 17

njordan11

so, ammonia would be pyramidal but ammonium tetrahedral?? thanks!! :smile:

Reply 18

intellectual1

3

Mass Spectrometer questions have'nt featured much at all...could they?

Reply 19

intellectual1

3

Original post by INeedToRevise

Have you got the Jan 2011 markscheme??

There was a thread posted by someone with all the Jan11 papers...its in Chemistry forums somewhere...
Jan10 was a hard paper, Jun10 was an easy paper, Jan11 was a hard paper, so I guess we'll have a medium to easy level of difficulty on Monday hmmm

Definitions are very easy marks...
Calculations are usually worth alot of easy marks if you know how to do them :wink:

Oxidation numbers
Redox
Halogens
Group 1 and 2
Shapes of molecules/ions
Electronic configuration of atoms and ions

This is a unit which almost every person does at least twice, so we can expect high boundaries if it is an easy paper.

(edited 12 years ago)

OCR F321 - 23rd May

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