[IWantSomeMushu]

I need to work on my calculations lol.

[Big-Daddy]

(Original post by HerroKitty)
Anyone know if the markscheme for the IGCSE Sample Assessment Material Paper (first examination June 2013) is wrong?

One of the questions about electrolysis says Name the product formed at the Anode and Cathode during the electrolysis of Copper Chloride. Apparently at the Anode Copper is formed and at the Cathode Copper is formed?

Copper is obviously not formed at both the anode and the cathode ... I seriously doubt that the mark scheme says that.

I see - the mark scheme says copper is formed at the anode and chlorine at the cathode.

Yes, this is wrong. Copper is formed at the cathode and chlorine at the anode.

[Big-Daddy]

(Original post by IWantSomeMushu)
I need to work on my calculations lol.

Just remember:

Mass = Moles * Mr
Volume = Moles * Molar Volume (24 mol^(-1)dm^3 unless otherwise stated)
Moles = Concentration * Volume

Volume is measured in dm^3, moles in mol, mass in g, Mr in gmol^(-1), molar volume in mol^(-1)dm^3 and concentration in moldm^(-3).

Apart from that, there are the electrolysis calculations. If you can't do them, just hope they don't come up.

[nitrome]

please can someone explain to me how the rate and yield changes with pressure temperature catalyst etc?

[SupremeNunchucks]

Guys will moles calculations come up on paper 1?

[IWantSomeMushu]

(Original post by Big-Daddy)
Just remember:

Mass = Moles * Mr
Volume = Moles * Molar Volume (24 mol^(-1)dm^3 unless otherwise stated)
Moles = Concentration * Volume

Volume is measured in dm^3, moles in mol, mass in g, Mr in gmol^(-1), molar volume in mol^(-1)dm^3 and concentration in moldm^(-3).

Apart from that, there are the electrolysis calculations. If you can't do them, just hope they don't come up.

Ah, cheers for that.

Gonna go and practice some

[NilFBosh]

Could someone solve this pls!!

Potassium hydrogen carbonate reacts with dilute hydrochloric acid.

An experiment was set up to find the enthalpy change of this reaction. The experimental data are given below.

Mass of potassium hydrogen carbonate used = 2.00g

Initial Temperature of HCl = 27 C

The volume of HCl solution = 30 cm3

Final temperature of the solution = 22.1 C

*The density and the specific heat capacity are the same as those of water.

[Carmeee]

HELP
can anyone tell me what is methylbenzene used for???
thanks

[Pretending2study]

The Chemistry O level 2012 January paper 1 and 2 anyone?

[Clare2012]

For chemistry tomorrow two questions...

- does everyone know all of the different electrolysis equations e.g. brine/aqueous/molten etc. as i just cant remember it all???

- is the electrolysis calculations people were talking about triple???

Thanks

[eebootwo]

Does anyone know all of the reactions we have to know and their conditions... like catalytic cracking, the contact process and the hydration of ethene? What other equations and processes are there that we have to learn?

[Clare2012]

(Original post by Carmeee)
HELP
can anyone tell me what is methylbenzene used for???
thanks

Methylbenze is an organic solvent know as a toluene. When HCl(g) [hydrogen cholride gas] is dissolved in methybenzene the acidic properties are not shown (if there is no water present). This means damp red litmus doesnt turn blue, it wont react with Mg to form hydrogen and it wont react with marble chips.

Basically it couteracts the acidic properties of HCl

[nithpriya]

(Original post by eebootwo)
Does anyone know all of the reactions we have to know and their conditions... like catalytic cracking, the contact process and the hydration of ethene? What other equations and processes are there that we have to learn?

Haber process, electrolysis equation (H+ +2e->H2(g))

Metal Carbonate + Acid -> Salt + Water + Carbon Dioxide
Metal Oxide + Acid -> Salt + Water
Metal + Acid -> Salt + Hydrogen

Makin iron(blast furnace)

I think these are SOME of the others!!

[eebootwo]

(Original post by nithpriya)
Haber process, electrolysis equation (H+ +2e->H2(g))

Metal Carbonate + Acid -> Salt + Water + Carbon Dioxide
Metal Oxide + Acid -> Salt + Water
Metal + Acid -> Salt + Hydrogen

Makin iron(blast furnace)

I think these are SOME of the others!!

Sorry, I meant the Haber Process, extraction of Aluminium, catalytic cracking etc.- the stuff we have to learn catalysts and conditions for.

[member963009]

(Original post by NilFBosh)
Could someone solve this pls!!

Potassium hydrogen carbonate reacts with dilute hydrochloric acid.

An experiment was set up to find the enthalpy change of this reaction. The experimental data are given below.

Mass of potassium hydrogen carbonate used = 2.00g

Initial Temperature of HCl = 27 C

The volume of HCl solution = 30 cm3

Final temperature of the solution = 22.1 C

*The density and the specific heat capacity are the same as those of water.

Enthalpy change = mass of solution x change in temp x specific heat capacity of water

mass of solution: 30 g
temp change: 27-22.1 = 24.9

so enthalpy change: 30 * 24.9 * 4.2 (specific heat capacity of water)
=3137

(Original post by nitrome)
please can someone explain to me how the rate and yield changes with pressure temperature catalyst etc?

Rate increases with temperature as the molecules collide more often and more energy so there is an increased chance of collisions happening with the required activation energy meaning that the frequency of successful collisions increases. It increases with a catalyst as the catalyst provides a alternate pathway with a lower activation energy meaning more collisions that take place have the required activation energy meaning that the frequency of successful collisions increases. Pressure (when reacts gases) forces more of them together in the given volume so it kind of acts like concentration. That means in a given volume there are more reactants meaning there will be more successful collisions per second.

Yield (presumably you're talking about this in the context of reversible reactions in equilibrium) increases with more pressure if the products have less moles than the reactants e.g. N2 + 3H2 --><-- 2NH3 where reactants have 4 moles and the products only have 2. The previous example is exothermic so I like to write exothermic equations like this: (and vice versa) N2 + 3H2 --><-- 2NH3 + heat. Here is the temperature is increased the equilibrium will shift to the left, decreased yield. Catalyst has no effect no yield, it just speeds up the closed container obtaining equilibrium. Hope this helps!

[member963009]

(Original post by SupremeNunchucks)
Guys will moles calculations come up on paper 1?

yes

(Original post by Clare2012)
For chemistry tomorrow two questions...

- does everyone know all of the different electrolysis equations e.g. brine/aqueous/molten etc. as i just cant remember it all???

- is the electrolysis calculations people were talking about triple???

Thanks

You don't need to memorise them.
Yes electrolysis equations are only for the triple award

[NilFBosh]

(Original post by sahajkaur)
Enthalpy change = mass of solution x change in temp x specific heat capacity of water

mass of solution: 20 +2 = 22 g
temp change: 27-22.1 = 24.9

so enthalpy change: 22 * 24.9 * 4.2 (specific heat capacity of water)
=2301

Actually its 30+2, but my teacher said not to take the total mass of the solution as 32. We are supposed to take 30? Help?

[ak2109]

I assume electrolysis calculations won't come up tomorrow? All of the papers I have done have them appearing in paper 2.

[member963009]

(Original post by eebootwo)
Does anyone know all of the reactions we have to know and their conditions... like catalytic cracking, the contact process and the hydration of ethene? What other equations and processes are there that we have to learn?

1) Contact process for the second reaction where :

2SO2 + O2 --><-- 2SO3
Temp: 400-500° C
Catalyst: Vanadium (V) Oxide
Pressure: 2 atm

2) Haber process:
Temp: 400-500° C
Catalyst: Iron
Pressure: 200 atm

3) Catalytic cracking:
Catalyst: Aluminium Oxide/Silica
Temp: 600-700 ° C

4) Dehydration of Ethanol:
Catalyst: Hot Aluminium Oxide

5) Fermentation:
Temp: 25-40 ° C

6) Direct Hydration of Ethene:
Temp: 300° C
Pressure: 60-70 atm
Catalyst: Phosphoric acid

That's it

[Pretending2study]

Can anybody gimmi a link for the Jan 2012 papers?