AQA CHEM5 A2 Chemistry - 19th June 2013

http://filestore.aqa.org.uk/subjects/AQA-CHEM5-W-QP-JAN10.PDF



7) For that very last question , how does the graph actually look? I have drawn a graph , but i don;t know if that would pick up the marks?

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http://www.chemguide.co.uk/physical/catalysis/introduction.html

the graph looks like the one at the bottom of this page

http://www.chemguide.co.uk/physical/catalysis/introduction.html

the graph looks like the one at the bottom of this page

Ok cool...so are u aiming for an A star grade in the summer?

http://filestore.aqa.org.uk/subjects/AQA-CHEM5-W-QP-JAN10.PDF


1) In 1ci ) , for the equation 2 that they are asking , would they accept,
V2O4 + 1/2 O2 --> V2O5
yep i think they would allow it
because in the MS they have actually doubled it all up?

2) In question number 3c ) is my answer , given below, right?

Pt (s) /H2(g) /H2O (l) // O2 (g) / OH- (aq) / Pt (s)

Pt|H2(g)|OH-(aq),H2O(l)||O2(g)|H2O(l),OH–(aq)|Pt this is the right answer but you can also have :
pt (s)| h2(g)|oh-(aq)||o2(g)|(oh-)|pt ( this is without water you dont have to include water)
yours equation isnt right because the 1st h20 should be oh-



The MS is confusing me...

3) For 3h) would they accept my answer: Hydrogen could be produced by the electrolysis of water, and this requires electricity which is generated by burning fossil fuels. This burning of fossil fuels will release CO2 into the envt. think this would be fine but i would also mention that electrolysis isnt carbon neutral

4) For 6a) would you get the second mark , with a wrong product?
not sure about this one sorry
5) Pls can u explain the calculation question in 8c ?
i explained this in the post above

6) For 9a) would this get 3 marks for the colours explanation?

Ti (III) ions are coloured because it has got partially filled 3d orbitals. Therefore, d-d transitions can take place which means electrons are excited from ground state to higher energy level. Light is absorbed from the visible range. Ti (IV) has empty 3d orbitals. So no d-d electron transitions taking place. No light energy from visible range absorbed.
i think this would get you the marks
Would this get the marks, because the MS seems so different?

7) For that very last question , how does the graph actually look? I have drawn a graph , but i don;t know if that would pick up the marks?

phew and thanks!

equation for the reaction of sodium hydroxide with phosphoric acid:
H3PO4 + 3NaOH = Na3PO4 + 3H2O

moles of naoh = 0.5 x ( 21.2/1000) = 0.0106
moles of h3po4 used in titre = 0.0106/3 =3.53x10-3

however this is the moles in 25cm3 the tank has 25000 dm3
25cm3 = 25/1000 =0.0025dm3

ratio of volume in tank to volum titrated = 25000/0.025 =1x106

so the moles on h3po4 in tank will be 1x106 times that we used for the tiration
therefor moles of h3po4 in tank = 3.53x10-3 x 1x106= 3530 moles

now we need to find the moles of phosphorus oxide
equation for phosphorus oxide reacting with water to make phosphoric acid is:

P4O10 + 6H20 = 4H3PO4

we know the moles of h3po4 is 3530
moles of p4o10 = 3530/4 = 882.5 moles

find the mass of p4o10
mass = moles x mr
= 882.5 x 248 = 250630g
= 250630 / 1000 = 250.63kg

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A solution of iron(II) sulfate was prepared by dissolving 10.00 g of FeSO4.7H2O (Mr
= 277.9) in water and making up to 250 cm3 of solution. The solution was left to stand, exposed to air, and some of the iron(II) ions became oxidised to iron(III) ions. A 25.0 cm3
sample of the partially oxidised solution required 23.70 cm3 of 0.0100 mol dm–3 potassium dichromate(VI) solution for complete reaction in the presence of an excess of dilute sulfuric acid. Calculate the percentage of iron(II) ions that had been oxidised by the air.

In this pls can someone M5 to me , why do we need to perform the SUBSTRACTION. question 7d from June 2010 question paper.

Could someone please explain to me why exothermic reactions occur more spontaneously than less exothermic reactions (as in not as much heat given out) or endothermic reactions. Thanks

If the surface area of one of the electrode was doubled what impact would this have on the end?

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