OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012

snap! and yeah you got full marks

Lets get to the hard questions

1) determine if this reaction

ca(s) + o2 (g) gives cao (s) will this have a deta s of positive or negative and why ?

2)Is it true we always have to convert the degrees to kelvins or not and how do you convert Degrees to kelvins

-ve because entropy has decreased.

and yes we have to convert degrees to kelvin and say you had x degrees, you do x + 273 and = temp in kelvins.


1) what reaction is it called when cu2+(aq) + 2oh(aq) ----> cu(oh)2(s)
and has the entropy increased or decreased?

2) what colour is shown in the reaction above and which reaction gives a rusty brown precipitate?

Dw the exam is 2 hours!

What actually are the hydrogen fuel cell equations? Like at each electrode? Because right now I think they're:
h2 +2OH- ---> 2h2O +2e
0.5 O2 + h2O + 2e ---> 2OH-
But in a paper they had the first one the opposite way round...but that makes no sense...asdihaosidjaos heeeelp

For an alkaline fuel cell those are correct.

correct full marks
1) precipitation reaction , the entropy value decreased because there it goes from a diordered system to a more ordered system , and because there are mole number of moles on L.H.S then on R.H.S
2) from pale blue solution to deep blue , Fe3+

brilliant questions where answered perfectly except the colour change, it should be pale blue solution to pale blue precipitate

can i ask in the exam if we get the colours right but we put the wrong like pale deep will they still allow it or not?

i wanted to query about that if we get the colours right blue but forget or put wrong like pale/deep will we still lose the mark or will they give us a B.O.D mark?

How can transition metals act as catalysts(3)
Give three properties of transition metals (3)

ask me hard hard ok

-ve because entropy has decreased.

and yes we have to convert degrees to kelvin and say you had x degrees, you do x + 273 and = temp in kelvins.


1) what reaction is it called when cu2+(aq) + 2oh(aq) ----> cu(oh)2(s)
and has the entropy increased or decreased?

2) what colour is shown in the reaction above and which reaction gives a rusty brown precipitate?

sorry i dont really know?

1) they can acts as catalysts as they have variable oxidation states so they can be reduced and the oxidised to the state they started at without being used up in the reaction.
2) coloured compounds, variable oxidation states, take part in ligand substitution reactions

ok explain the biochemical importance of iron in haemoglobin, including ligand substitution?

1) is wrong but i thought the exact same thing at first its actually adsorption,chemical reaction and desorption
2) perfect 3/3

1) Iron in haemoglobin is important because the Fe2+ is attracted to oxygen and oxygen binds to Fe2+ and therefore this is ligand subsitution of oxygen. Ligand subsition is important as it allows oxygen to bind easier with haemoglobin. and due to K stab, allows more oxygen to be transported around the blood more faster and the structure is the fe2+ and globin is attracted to it with 3 oxygens sourrounding the fe 2+

sweeet! thanks for telling me!

and yeah your answer is right but i though only 1 o2 molecule bind to fe2+?

sorry i dont really know?

1) they can acts as catalysts as they have variable oxidation states so they can be reduced and the oxidised to the state they started at without being used up in the reaction.
2) coloured compounds, variable oxidation states, take part in ligand substitution reactions

ok explain the biochemical importance of iron in haemoglobin, including ligand substitution?

yep true one oxygen and 4 Nitrogens right with the globin right? so how many marks i got?

Question:- suggest why scientists use the 1.00x10-14 when calculating Kw (1)

For an alkaline fuel cell those are correct.

3/4

and is it because they assume it is at room temp and pressure?

yes that is what i was thinking as well and cause may be it is a whole number thats why they use it