***2013 LC Chemistry Before/After***

Glee_GG

Are the winkler reagents Manganese sulfate and potassium iodide or manganese sulfate and sulfuric acid?

MarieCurie22

Glee_GG wrote: »

Are the winkler reagents Manganese sulfate and potassium iodide or manganese sulfate and sulfuric acid?

Manganese sulfate and alkaline potassium iodide

Glee_GG

MarieCurie22 wrote: »

Manganese sulfate and alkaline potassium iodide

Cheers, wrote them both down in my book and had them both crossed out!

MarieCurie22

oooh lads i like the look of 2009 q3 if i were an examiner id be asking that again

MarieCurie22

MarieCurie22 wrote: »

Also you guys would be idiots (not saying you are yet :P) if you go into the exam not knowing:
Mn+7 = purple
Mn+4 = brown
Mn+2 = colourless

You add H2SO4 to provide protons to enure complete redution of Mn+7 to Mn+2 NOT Mn+4
Mn+4 is in the BOD expriment its the brown percipitate...
Mn+2 is a catalyst (autocatalysis!)

We add conc H2SO4 to get rid of the Brown ppt in the experiment and liberate iodine right?

Glee_GG

Should be my best exam so not that worried about this, have a feeling experiments are going to be pretty hard seeing as last years were just beautiful in all fairness! Have a feeling anion testing is going to make a sneaky appearance, once the soap experiment stays away should be ok.

MarieCurie22

MarieCurie22 wrote: »

oooh lads i like the look of 2009 q3 if i were an examiner id be asking that again

Anion tests scare me that needs to stay away!

MarieCurie22

Deleted User wrote: »

Anion tests scare me that needs to stay away!

Ok heres 2 out of the way:

Test for a chloride ion:
Princess chloride is trapped in an aqueous solution...
Along come sliver knight (silver nitrate) to rescue her
They then try escape on his white horse percipitate...
But the evil queen dilute ammoniam returns! and they dissappear and drown

Parawhore.xD

MarieCurie22 wrote: »

Ionisation Energy:
The energy required to remove the most loosely bound electron from a neutral atom in its gaseous state.

Ionisation energies....
-Increase across the period:
-Due to the decrease in atomic radius (See above)
-Increase in atomic charge (more protons)
-Decrease down the period:
-Due to increasing atomic radius.
-Screening effect of inner electrons!

You haven't accounted for the interruption of the increase across groups 1&2 and 5&6 because of the half filled sublevels increased stability.

MarieCurie22

Sulfate and Sulfite:
Sulfate and sulfite are twin brothers walking in the woods...
They come across a bear (Barium chloride) and "poop" themselves (white percipitate)
Then sulfite remembers the Hyrogen Courage Liquid (HCl) in back pocket...
He shares it with his brother...
However Sulfite disappears and runs like the wind (ppt goes)
His brother doesnt seem to gain any courage and stands there frozen forever (ppt stays!)

MarieCurie22

MarieCurie22 wrote: »

Sulfate and Sulfite:
Sulfate and sulfite are twin brothers walking in the woods...
They come across a bear (Barium chloride) and "poop" themselves (white percipitate)
Then sulfite remembers the Hyrogen Courage Liquid (HCl) in back pocket...
He shares it with his brother...
However Sulfite disappears and runs like the wind (ppt goes)
His brother doesnt seem to gain any courage and stands there frozen forever (ppt stays!)

If only there was a story for them all!

Hamza Malik

So as a last minute study attempt, what question 3 experiment should I revise?

MarieCurie22

Phosphate:
Goes canary yellow! Ammonium Molybdate sounds to me like an exoctic bird so it must have something to do with canaries!
Cannaries fly but the acid we want is in the ground in fertilizer (occasionally) so it must be nitric acid!

Parawhore.xD

MarieCurie22 wrote: »

Sulfate and Sulfite:
Sulfate and sulfite are twin brothers walking in the woods...
They come across a bear (Barium chloride) and "poop" themselves (white percipitate)
Then sulfite remembers the Hyrogen Courage Liquid (HCl) in back pocket...
He shares it with his brother...
However Sulfite disappears and runs like the wind (ppt goes)
His brother doesnt seem to gain any courage and stands there frozen forever (ppt stays!)

I'm sorry...what?!

MarieCurie22

Hamza Malik wrote: »

So as a last minute study attempt, what question 3 experiment should I revise?

A quick look over:
Anions (see above) and flame tests
Rates of rxn (aLL)
equilirbrium and
those dodgy water ones! like chlorine in h20 (NB hypochlorous acid!!!!)

Hamza Malik

What are the conditions necessary for a dust explosion? :eek:

Prodigious

Dust!

MarieCurie22

Hamza Malik wrote: »

What are the conditions necessary for a dust explosion? :eek:

Easy peasy calm!!!
-Enclosed space
-Flamable dust
-A spark/ignition....

Hamza Malik

Hamza Malik wrote: »

What are the conditions necessary for a dust explosion? :eek:

High volumes of small particles?

Parawhore.xD

[Deleted User] wrote: »

High volumes of small particles?

It's high concentration either I think?

MarieCurie22

Parawhore.xD wrote: »

It's high concentration either I think?

Guys its CONDIOTIONS
the dust must be flammable yes when we say dust we mean finely ground particles in high concentration but you need it to be flammable or else it wont explode...
you also need an enclosed space for this to occur at all
and an ignition to start it all off!

SecondMan

MarieCurie22 wrote: »

Guys its CONDIOTIONS
the dust must be flammable yes when we say dust we mean finely ground particles in high concentration but you need it to be flammable or else it wont explode...
you also need an enclosed space for this to occur at all
and an ignition to start it all off!

You don't be playing with dust silos Mrs Curie! A science experiment already got the better of you before..*cough*radiation*cough*

Parawhore.xD

MarieCurie22 wrote: »

Guys its CONDIOTIONS
the dust must be flammable yes when we say dust we mean finely ground particles in high concentration but you need it to be flammable or else it wont explode...
you also need an enclosed space for this to occur at all
and an ignition to start it all off!

I'm well aware it's conditions plural, no need to take on such a condescending tone thanks.

Hamza Malik

Eek does the intermediate formation theory explain homogeneous, heterogeneous or autocatalysis ?

MarieCurie22

Parawhore.xD wrote: »

I'm well aware it's conditions plural, no need to take on such a condescending tone thanks.

I was trying to help you...

MarieCurie22

Hamza Malik wrote: »

Eek does the intermediate formation theory explain homogeneous, heterogeneous or autocatalysis ?

Homogenoous.....they have to be in the same phase for intermediate compounds to form...

Heterogenous is....surface adsorbtion...

Parawhore.xD

MarieCurie22 wrote: »

I was trying to help you...

If I want help I'll ask for it.

Hamza Malik

MarieCurie22 wrote: »

Homogenoous.....they have to be in the same phase for intermediate compounds to form...

Heterogenous is....surface adsorbtion...

ill surely get an A1 now

Scuid Mhór

Parawhore.xD wrote: »

If I want help I'll ask for it.

Ohhhhhhhhhhhh

SecondMan

Parawhore.xD wrote: »

If I want help I'll ask for it.

Tension in the forum,
Let the tension free,
We all jump up in a one, two, three.

MarieCurie22

SecondMan wrote: »

Tension in the forum,
Let the tension free,
We all jump up in a one, two, three.

There is no tension :P...at least not on my part idc what she has to say

Prodigious

SecondMan wrote: »

Tension in the forum,
Let the tension free,
We all jump up in a one, two, three.

Try not to be a bollix for once? They're clearly stressed...

MarieCurie22

Prodigious wrote: »

Try not to be a bollix for once? They're clearly stressed...

Iim not stressed XD im currently in bed just reading eating yoghurt XD

SecondMan

Prodigious wrote: »

Try not to be a bollix for once? They're clearly stressed...

**** you! I've a Chemistry exam too. Im trying to calm things here but nooooo little Prodgy takes things too seriously and likes seeing people stressed.

Hamza Malik

Yep, you guys are losing it.

Parawhore.xD

SecondMan wrote: »

Tension in the forum,
Let the tension free,
We all jump up in a one, two, three.

I'm not tense, I'm buzzing :P

I'm going to assume it's just a case of tone not travelling well over the Internet, I gain nothing from this exchange anyway.

Fert94

Chillax people, let the results do the talking in August if you're that intent on antagonising people :P no amount of narkiness is going to help anybody!

Scuid Mhór

Can't you see all this fighting is tearing us apart?

Fert94

Scuid Mhór wrote: »

Can't you see all this fighting is tearing us apart?

Think of the children...

Scuid Mhór

MarieCurie22 wrote: »

Iim not stressed XD im currently in bed just reading eating yoghurt XD

Leave the yoghurt out of it MarieCurie22!

lizardspock

Why does Fehling's solution have to be made up fresh on the day?? anyone?

MarieCurie22

lizardspock wrote: »

Why does Fehling's solution have to be made up fresh on the day?? anyone?

The solution will be oxidised by the air

Prodigious

MarieCurie22 wrote: »

The solution will be oxidised by the air

And becomes explosive?

MarieCurie22

Prodigious wrote: »

And becomes explosive?

No? Not that I know of?

lizardspock

Prodigious wrote: »

And becomes explosive?

Think that's for Tollen's reagent

MarieCurie22

For equilibrium calculations when do we count the volume of the vessel?

MarieCurie22

MarieCurie22 wrote: »

For equilibrium calculations when do we count the volume of the vessel?

If it's over 1L. Calculations are based on molarity

MarieCurie22

do we need the 3 equilibrium experiments or will one do?

Guys, why is it that we don't make octane number of petrol 100?

SecondMan

MarieCurie22 wrote: »

do we need the 3 equilibrium experiments or will one do?

Probably better off studying one in detail and briefly look through the other two in case they ask a direct question about one of the experiments.