• We have a few events lined up for the October school holidays!
    Watch this space...

Q17 (1 Viewer)

k4t5UM0t0

New Member
Joined
Mar 6, 2007
Messages
19
Gender
Male
HSC
2007
I hated that flame test question: i wrote it wasn't suitable because it is used to identify cations, sodium carbonate will be distinguishable as is barium nitrate though lead nitrate and HCl would be unidentifiable, hence wouldn't be suitable as the only method used.
 

codyjh

New Member
Joined
Oct 27, 2006
Messages
16
Gender
Male
HSC
2007
1)sodium carbonate
2)HCL
3)lead nitrate (i think)
4)barium nitrate (i think)

not sure if i put 3 and 4 in the right spot :s . least ill get 1 /2 lol
 

codyjh

New Member
Joined
Oct 27, 2006
Messages
16
Gender
Male
HSC
2007
k4t5UM0t0 said:
I hated that flame test question: i wrote it wasn't suitable because it is used to identify cations, sodium carbonate will be distinguishable as is barium nitrate though lead nitrate and HCl would be unidentifiable, hence wouldn't be suitable as the only method used.

yeah i said something like that. not all the solutions would of given a colour ie: hcl and barium nitrate. people were sayin shit like if would of been toxic with the lead nitrate being vaporised. either way
 

dwatt

Member
Joined
Aug 7, 2004
Messages
68
Gender
Male
HSC
2007
codyjh said:
yeah i said something like that. not all the solutions would of given a colour ie: hcl and barium nitrate. people were sayin shit like if would of been toxic with the lead nitrate being vaporised. either way
Barium has a green flame colour. Because the other two cations also had flame tests, it should have been possible to deduce that the last was HCl (which has no flame colour like you say).

So I was pissed off with that question. You COULD flame test it. The reason it is unsuitable is because lead vapour is fairly toxic, which it is not on the syllabus for the list of flame colours we are supposed to be testing.

Still...could have done it in a fume cupboard.
 

xclusv2bhung

sexier than neha x10000
Joined
Dec 26, 2006
Messages
1,347
Location
Sydney
Gender
Male
HSC
2007
aww damn :

i did
HCl
sodium carbonate
lead nitrate
and other nitrate.

aww damnit .. but i kinda guessed the last two.
 

aja152

Member
Joined
Aug 18, 2006
Messages
41
Gender
Undisclosed
HSC
N/A
damn..... i got the whole thing wrong.................................grr
 

codyjh

New Member
Joined
Oct 27, 2006
Messages
16
Gender
Male
HSC
2007
dwatt said:
Barium has a green flame colour. Because the other two cations also had flame tests, it should have been possible to deduce that the last was HCl (which has no flame colour like you say).

So I was pissed off with that question. You COULD flame test it. The reason it is unsuitable is because lead vapour is fairly toxic, which it is not on the syllabus for the list of flame colours we are supposed to be testing.

Still...could have done it in a fume cupboard.
yeah my bad

but how were we sposed to no the Pb2+ cations had a distinctive colour when i cant find it in and text book :s . only has precipitate tests. or were spose to assume that all metal ions produce a distinctive colour? BOS may take both answers ? :S confused lol

spose its only 1 mark... right?
 

codyjh

New Member
Joined
Oct 27, 2006
Messages
16
Gender
Male
HSC
2007
dwatt said:
Barium has a green flame colour. Because the other two cations also had flame tests, it should have been possible to deduce that the last was HCl (which has no flame colour like you say).

So I was pissed off with that question. You COULD flame test it. The reason it is unsuitable is because lead vapour is fairly toxic, which it is not on the syllabus for the list of flame colours we are supposed to be testing.

Still...could have done it in a fume cupboard.
yeah my bad

but how were we sposed to no the Pb2+ cations had a distinctive colour when i cant find it in and text book :s . only has precipitate tests. or were spose to assume that all metal ions produce a distinctive colour? BOS may take both answers ? :S confused lol

spose its only 1 mark... right?
 

conman

Member
Joined
May 2, 2005
Messages
139
Location
West of Sydney
Gender
Male
HSC
2007
All the carbonates will be precipitated so we can Na2C03 to be the one which cause 2 precipitation reactions and the rest are easy. HCl will react with Pb2+ to precipitate so leaving out BaC03 alone.
 

mzduxx2006

Member
Joined
Mar 18, 2007
Messages
324
Location
MERRYLANDS
Gender
Female
HSC
2007
Tmer said:
please help me solve it;
you had:
HCl
sodium carbonate
barium nitrate
lead nitrate

this is what i did in the exam but i got confused:
1+2= gas released (HCl and sodium carbonate, first thought)

2+4= no reaction
now from my first thought, 2 is either the acid or the carbonate...
barium nitrate + HCl gives no reaction so its possible
and now (1=sodium carbonate, 2= acid, 4=barium, only thing left is 3, = lead)

but...
3+4 = white precipitate? lead nitrate and barium nitrate definitely do not react...

this is probably all wrong now... any1 confident with their answer?
1 i had HCL

2 i had sodium

3 i had lead

4 i had barium

Pft probly not right but HEYY NO CHEMISTRYYYYYY EVERRRRR AGAIN :D
 

mzduxx2006

Member
Joined
Mar 18, 2007
Messages
324
Location
MERRYLANDS
Gender
Female
HSC
2007
k4t5UM0t0 said:
I hated that flame test question: i wrote it wasn't suitable because it is used to identify cations, sodium carbonate will be distinguishable as is barium nitrate though lead nitrate and HCl would be unidentifiable, hence wouldn't be suitable as the only method used.
um i said someshit like flame tests are only suitable for identifying cations not anions. is that right?
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top