F321 - Atoms, Bonds and Groups - June 2010 OCR A Post Examination Discussion

Exam went underway at 1:30pm. How did every1 find it?

I found it EASY, have a feeling grade boundaries are gonna go up.

Anyone find any questions in specific hard? Share your thoughts!

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Reply 1

greenford

juman786

Exam went underway at 1:30pm. How did every1 find it?

I found it EASY, have a feeling grade boundaries are gonna go up.

Anyone find any questions in specific hard? Share your thoughts!

I thought the paper was quiet difficult to be honest... there hasn't been a paper like this in previous years....

There was these two question..
1) Calculate the percentage, by mas.........
2) 2 ions of H2S04

Reply 2

terry_2006

for ions one do you think i will lose mark if is:
H2SO4(s)+aq--->2H+ +SO4^-2

Reply 3

hardz21

terry_2006

for ions one do you think i will lose mark if is:
H2SO4(s)+aq--->2H+ +SO4^-2

i wrote this. i think i will lose a mark. if it was out of 2, maybe 1 mark.

Reply 4

greenford

I definitely know that H+ was one of the ion... dont know about the other one....
can any of you remember that percentage composition by mass question?

I hope the grade boundaries are low

Reply 5

x_katie

personally i think it was harder than a lot of the papers, and certainely some unexpected questions popped up. think i got silly answer for the atoms in the shield one.. :s and didn't get the ions either. put H+, but didn't know the other..

Reply 6

greenford

how did you guys find the paper overall??????????

Reply 7

dilbox

hmmm guys I got 9 point something percent i think for the percentage by mass....others obtained 98 point something percent.....maybe I missread my calculator :| can anyone give me a second opinion with there awnser? The paper overall was really good :biggrin:

Reply 8

Josh-H

Seemed a hard paper to me, think I did ok though.

Reply 9

Kaph

greenford

I definitely know that H+ was one of the ion... dont know about the other one....
can any of you remember that percentage composition by mass question?

I hope the grade boundaries are low

I got 98.4% or something.

Reply 10

terry_2006

What will me the definition for orbital? I put : it is a region of where electrons oscillate.

Reply 11

CertifiedAngel

terry_2006

What will me the definition for orbital? I put : it is a region of where electrons oscillate.

I wrote: A region that can hold up to two electrons with opposite spins.
Think thats right.

It was okay. Definately harder than last years papers though!

Reply 12

BackDoorEntry

terry_2006

What will me the definition for orbital? I put : it is a region of where electrons oscillate.

I put the region of an atom where you are more than 99.9% likely to find a given electron

Reply 13

terry_2006

Does anyone have the paper or do you know if the question about percentage? I can't remember whether it asked for percentage of purity or impurity. Can anyone justify ? I thought i read was the purity but my classmate says the otherway.

Reply 14

shdw101

THAT EXAM WAS HARD
what did you guys get for the empirical formula for Sn Oxide?

Reply 15

terry_2006

the old mark scheme for 2001 june answer for orbital definiton was: a region where electron can be found.
I guess i will get the mark then :>

Reply 16

steph_v

shdw101

THAT EXAM WAS HARD
what did you guys get for the empirical formula for Sn Oxide?

SnO2 I thought that was an easy questions, but a lot of the paper was difficult.

Reply 17

terry_2006

Sn Mr=118.7gmol^-1 percentage of Sn was 78.8% and O:100-78.8=21.2
O=16.0g

Sn : O
78.8 21.2
----- -----
118.7 16.0

0.66 : 1.325
1 : 2

SnO2 should be the empircal formula.

Reply 18

terry_2006

There was a question that i had to think about
The aluminium one, when i first read it was weird.

Reply 19

Dr WestwooDD

F321 ~ Unofficial Mark Scheme

Here are my answers to Question 1:

a) 50 68 50 ~ proton, neutrons and electrons of Tin (Sn)

b) The weighted mean mass; of an atom of an element compared; to 1/12th of the carbon-12 isotope;

c) 118.42

d) 1.05 x10^25

e) 78.8% of Sn and 21.2% O2; therefore SnO2

Here are my Question 2 answers:

a) H+ and SO4 2-

b) bubbles/fizzing of gas (CO2); solid carbonate dissolves;

K2CO3 + H2SO4 = K2SO4 + CO2 + H2O;

c) 2.47 x 10^-3

d) 4.94 x 10^-3

e) 98.4%

Here are my Question 3 answers:

a) 3d then 4s

b) Orbital~ where two electrons 'spin'; opposite directions; eq

c) 11 electrons in p-orbitals

d) Ca 2+ = 18 electrons

e) Am not too sure; lead to believe it is 2nd, 3rd, 10th and 11th

f) Al (2+) (g) = Al (3+) (g) + e-

Here are my answers to Question 4:

a) purple/violet; orange

b) displacement between Br and I; eq

c) Cl simultanously oxidised and reduced;

From 0 to +1 in HClO;
From 0 to -1 in HCl;

d) thermal decomposition

e) Calculation involving a carbonate; find volume of CO2;

I cannot really remember what my answer was; something like 17.4dm3

f) Thermal stability increases down the group; eq

Here are my answers to Question 5:

a) Lithium has giant metallic structure; diagram etc;

Fixed cations; surrounded by delocalised electrons; tightly packed/strong attractions; eq ~ high boiling point

b) Fluorine covalently bonded; 8 electrons for each one [ 3 x lone pair]; one shared pair; eq

c) LiF ~ Ionic structure ~ Li electron in outer shell completes the incomplete shell to leave Li with a full shell; and a + charge []; F with a full shell (show by dots and crosses); and a - charge []; eq

d) Fails to conduct when solid; ions are fixed; conducts when molten; ions are delocalised;

e) 2 + 3[F2] = 2[BF3]

f) Trigonal planar; 120 degrees; 3 bonded pairs and no lone pairs; eq ~ repulsion theory explained; eq

g) Permeanent dipoles arise due to difference in electronegativity; F very electronegative; electrons pulled closer; eq

h) Atomic radii decrease across period 2; increased proton number; therefore increased nuclear charge; electrons added to same shell; similar shielding; hence atomic radii decrease; shells/electrons pulled closer/more strongly to nucleus; ionisation increases; eq