Equilibria, Energetics and Elements (F325) - June 2011 Exam.

Reply 960

786girl

Original post by arvin_infinity

-ve

what time is the exam on!? 1:30 wednesday!?

thanx
erm mine starts at 1.30

Reply 961

786girl

what COLOURS do we need to know? Can someone give me a list so i can just learn it. isit the precipitation ones ?

Reply 962

apo1324

11

Original post by 786girl

what COLOURS do we need to know? Can someone give me a list so i can just learn it. isit the precipitation ones ?

Precipitation Reactions involving Transition Metals:-

Copper(II) Ions + NaOH(aq) : Pale blue solution. - - > Pale blue precipitate.

Cobalt(II) Ions + NaOH(aq) : Pink solution. - - > Blue precipitate.

Iron(II) Ions + NaOH(aq) : Pale green solution. - - > Green precipitate.

Iron(III) Ions + NaOH(aq) : Pale yellow solution. - - > Rusty-brown precipitate.

Ligand Substitution:-

Copper(II) Ions with ammonia: Pale blue solution. - - > Deep blue solution.

Copper(II) Ions with conc HCl : Pale blue solution. - - > Yellow solution.

Cobalt(II) Ions with conc HCl : Pink solution. - - > Blue solution.

:smile:

(edited 12 years ago)

Reply 963

iforgotmyusername

Is the gradient on a rate concentration graph of first order reaction equal to k (rate constant)?

Reply 964

iforgotmyusername

Original post by 786girl

what COLOURS do we need to know? Can someone give me a list so i can just learn it. isit the precipitation ones ?

print off spec from ocr website, tells you exactly which colours to learn.

Reply 965

darkiee

10

I am doing 24hrs revision to make a Grade difference

Reply 966

Killmepls

10

Guys I have a feeling they could ask us to draw a hydrogen fuel cell, how do you do that :colondollar:

I know one half cell will be H2 gas and H+ ions right with pt electrode right? What about the other?

Reply 967

KateSW

Original post by 786girl

what COLOURS do we need to know? Can someone give me a list so i can just learn it. isit the precipitation ones ?

You may have found out already, but I found this on the specification:
"describe, including ionic equations, the simple precipitation reactions and the accompanying colour changes of Cu2+(aq), Co2+(aq), Fe2+(aq) and Fe3+(aq) with aqueous sodium hydroxide"

So I think these are the colours:

Solution --> Precipitate
Cu2+ Light blue --> Dark blue
Co2+ Pink --> Blue
Fe2+ Pale green --> Dark Green
Fe3+ Yellow --> Orange / Brown

(edited 12 years ago)

Reply 968

darkiee

10

Original post by Killmepls

Guys I have a feeling they could ask us to draw a hydrogen fuel cell, how do you do that :colondollar:

I know one half cell will be H2 gas and H+ ions right with pt electrode right? What about the other?

Its just one, when they ask you to Draw a standard lets say copper half cell, that when you draw it with Hydrogen and copper, get it?

Reply 969

volvicstar

what is the equation for calculating H+ from a buffer system?
what is the general ionic equation for neutralisation?
what does a more negative electrode potential show?
outline how you would carry out a redox titration using MnO4-?

Reply 970

Flux_Pav

hey guys
came across neutralization and saw the page in the book
what if the number of moles of the acid and alkali are not the same? if that happens, which one of the two moles do you take?
and also, what if say 3 moles of water are being formed , what do you do then?
+ rep

Reply 971

k256_93

[H+] = Ka x [HA]/[A-]
Neutralisation : H+(aq) + OH-(aq)-> H2O(l)
A more negative electrode potential shows that that system is more likely to donate electrons compared to a more positivise one.

Reply 972

darkiee

10

Original post by Flux_Pav

hey guys
came across neutralization and saw the page in the book
what if the number of moles of the acid and alkali are not the same? if that happens, which one of the two moles do you take?
and also, what if say 3 moles of water are being formed , what do you do then?
+ rep

You add all the moles together, to give you a mass or something like that cant remember what my teacher said

Ignore this I am wrong I think

Reply 973

hellosarah

Original post by Pandit Bandit

how would you go about doing this question guys?

the 250 cm3 always throws me off!

What is the actual answer pleasee? (think i've got it wrong :/)

Reply 974

Pandit Bandit

Original post by hellosarah

What is the actual answer pleasee? (think i've got it wrong :/)

0.161 moldm-3 hmm i thought it woulde be 1.61

Reply 975

Killmepls

10

Original post by darkiee

Its just one, when they ask you to Draw a standard lets say copper half cell, that when you draw it with Hydrogen and copper, get it?

Nooo that's not what I mean, that's comparing a copper half cell to a standard hydrogen half cell.

A hydrogen fuel cell has hydrogen and oxygen reacting. Look at page 191 in text book, it has a simple diagram but I'm wondering could you draw that using two half cells? :\ You never know with OCR lol..

Reply 976

darkiee

10

Original post by Killmepls

Nooo that's not what I mean, that's comparing a copper half cell to a standard hydrogen half cell.

A hydrogen fuel cell has hydrogen and oxygen reacting. Look at page 191 in text book, it has a simple diagram but I'm wondering could you draw that using two half cells? :\ You never know with OCR lol..

Oh sorry I didnt read ur question properly, HYDROGEN FUEL CELL, i i thought u meant hydrogen half cell my fault.

Reply 977

haydyb123

9

Original post by Flux_Pav

hey guys
came across neutralization and saw the page in the book
what if the number of moles of the acid and alkali are not the same? if that happens, which one of the two moles do you take?
and also, what if say 3 moles of water are being formed , what do you do then?
+ rep

Hey Flux,
you if the moles are unbalanced you need to calculate how much it is in excess by:

say: .5 moles of HCl and 0.25 moles of of NaOH, you know that to form one mole of water from the stoichiometry of the equation your HCl is in excess by 0.25 (as it is 1:1 ratio) therefore when you're dividing your heat change by your moles, it will be 0.25 as oppose to 0.5 :smile:

Reply 978

hellosarah

Original post by Pandit Bandit

0.161 moldm-3 hmm i thought it woulde be 1.61

aaah whaaaaaaaaat?? I got 1.61 too??

:confused:

Reply 979

Flux_Pav

Original post by haydyb123

Hey Flux,
you if the moles are unbalanced you need to calculate how much it is in excess by:

say: .5 moles of HCl and 0.25 moles of of NaOH, you know that to form one mole of water from the stoichiometry of the equation your HCl is in excess by 0.25 (as it is 1:1 ratio) therefore when you're dividing your heat change by your moles, it will be 0.25 as oppose to 0.5 :smile:

oh thanks!
so you basically divide by how much there is in excess?
so say if u have a ratio thats 2:1 - acid:alkali would u multiply the excess amout by 2?

Equilibria, Energetics and Elements (F325) - June 2011 Exam.

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