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AS OCR chemistry B (SALTERS) F331 on the 15th may 2012

dirrane

Hey guys just wondering whose got a chem exam tomorrow,and are you guys ready for it, cos i am not :colondollar:

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Reply 1

Reina

No one is ever ready for chemistry exams :'(

Reply 2

craycray

I DO I DO I DO! I'm just starting revision now heh totes good time management right here :wink:

Reply 3

dirrane

does anyone know how to carry out an experiment, to test the thermal stability of groups 2.

Reply 4

xxZazxx

Done all the past papers about 5 times lol, but i did that last time and only got a C so hopefully this paper will be a bit easier lol

Reply 5

matty b

Original post by dirrane

does anyone know how to carry out an experiment, to test the thermal stability of groups 2.

Simply put equal amounts of carbonates of the Group 2 metals in separate tubes, with pipes connected to tubes with limewater in. Use Bunsen burners to heat the carbonates until they decompose, increasing the heat by slowly turning the flame blue. The time taken for the limewater to go "cloudy" should be recorded for each carbonate.

The quickest one to decompose will have the lowest thermal stability (ie MgCO3) and the longest will have the highest (ie BaCO3)

Hope it helps.

Reply 6

xxZazxx

Original post by dirrane

does anyone know how to carry out an experiment, to test the thermal stability of groups 2.

basically just the lime water going cloudy in the presence of CO2, so u know, heat the metal in a test tube over a bunsen burner, collect the gas given off in a gas syringe and feed the other end of the syringe into a test tube of lime water. refer to controls like same amount of metal, same volume of limewater, repeats etc. the longer it takes for the lime water to go cloudy the more thermally stable the metal, thermal stability increases down the group. that should be enough to get you the full marks

wow same time lol

Original post by dirrane

does anyone know how to carry out an experiment, to test the thermal stability of groups 2.

1) heat carbonate in a tube
2) pass gas through limewater
3) the limewater goes cloudy

Reply 9

StutZz

what do you guys think is likely to come up tomorrow?
Group 2 reactions is surely pending. :s

Reply 10

Bigyouth

(retaking)...

just out of curiosity...

may have found a mistake in the mark scheme.

"How many full orbitals are in an atom of sulfur?"

16 electrons

1s2, 2s2, 2p6, 3s2, 3p4

so that's 8 full orbitals..

mark scheme says 7..

have i made some kind of obvious mistake here? Or should we still doubt the integrity of exam boards...

Reply 11

Kreayshawn

i'm 90% sure sub orbitals are in f332 and not this exam

Reply 12

pilkins09

Original post by Bigyouth

its because in 3p4 the orbitals each have 1 electron in first, and then they fill up ie one has 2 electrons, other two orbitals have 1 electron each
so the mark scheme is correct this time!

Reply 13

Kreayshawn

can anyone explain to me what makes ions flow throw the acceleration area in a mass spec.?
also, how many marks is usually an A for these papers?

(edited 11 years ago)

Reply 14

dongonaeatu

Original post by Kreayshawn

can anyone explain to me what makes ions flow throw the acceleration area in a mass spec.?
also, how many marks is usually an A for these papers?

An electric field attracts the positively charged ions and this is what accelerates them

around 46

Reply 15

Kreayshawn

thanks.

for hess cycles, is it just always arrows pointing up from elements for formation and arrows pointing down for combustion?

Reply 16

Lily Academia

Can someone confirm it's PM? I have checked, double-checked and triple-checked my time table but I think I need reassurance :blush:

Reply 17

Salmonidae

Original post by Kreayshawn

thanks.

for hess cycles, is it just always arrows pointing up from elements for formation and arrows pointing down for combustion?

Yes arrows always pointing up for formation.
Also he's pointing down for combustion.
This is of course where the 'raw material' atoms are on the bottom, so watch out in the exam as they might swap it around to catch you out.