AQA CHEM5 A2 Chemistry - 19th June 2013

Scroll to see replies

It was along the lines of a complex is blue which means it absorbs red light, blue light has a higher freq. If we assume it becomes red by blue light absorbing it energy increase, decrease or stay the same.

The answer is that i would increase. E=HF, so an increase freq would obviously give a greater energy.

ye i remember puting that and saying frequency is proportional to the energy gap so higher frequency photons(blue) will increase the energy gap

Reply 2901

SexyAndIKnowIt.

Is there an unofficial mark scheme

Reply 2902

mulac1

nope - we need the paper...

Reply 2903

popnit

Original post by teen1234

2 factors that affect lattics dissociation:
charge of ions
size of ions
?

Thats exactly what i put

Posted from TSR Mobile

Reply 2904

khalidpatel

Original post by mulac1

haha good luck :smile:

right I'll try and have a go, firstly lets get all the questions - people will have to muck in and help though.
Q1: a) what is the perfect ionic model (1)
b) define 'standard enthalpy of lattice dissociation' (2)
c) Give 2 factors that affect the lattice enthalpy of dissociation (2)
d) calculate the lattice enthalpy of dissociation for AgBr (3)
e) How would you expect your value to 1d) to differ with that calculated from the PIModel. Explain (2)

Let's finish this unofficial markscheme

Posted from TSR Mobile

Reply 2905

Fergy94

I don't get why the hell they had to include y=mx+c, it's chemistry not maths!

Reply 2906

nimbusquaffle

Original post by popnit

Thats exactly what i put

Posted from TSR Mobile

i just put size and charge. do you think that would be okay? hopefully tha it was the ion would be implied :/

Reply 2907

Beth_L_G

Original post by cuckoo99

cant believe i get negged on here for quoting stuff from the textbook lolz if you wanna neg me atleast explain to me why im wrong "_"

People are really neg happy on this page. Just ignore them, you're being helpful to the rest of us :smile:

Reply 2908

PhoenixSeeker

Anyone know what the colour of [Ag(H2O)2]+ was?

Reply 2909

theslav

Original post by cuckoo99

ye i remember puting that and saying frequency is proportional to the energy gap so higher frequency photons(blue) will increase the energy gap

E=hv v is the frequency of light transmitted so if red light is transmitted then frequency is lower so E decreases

Reply 2910

Fergy94

Original post by PhoenixSeeker

Anyone know what the colour of [Ag(H2O)2]+ was?

I wrote colourless..

Reply 2911

cuckoo99

Original post by Beth_L_G

People are really neg happy on this page. Just ignore them, you're being helpful to the rest of us :smile:

cheers

Reply 2912

mchammer911

Questions i definitely screwed up on:
The q=mcdeltaT (5 marks) possibly got 1-2 marks
Balancing the p4o10 and naoh equation (1 mark)
That entropy change calculation (1 mark)
The cobalt catalyst equation (2 marks)
The last question about the ratios (5 marks) possibly got 1-2 marks

Any chance of me getting an A?

Reply 2913

PhoenixSeeker

Original post by Fergy94

I wrote colourless..

Did you put colourless going to colourless?

Reply 2914

cuckoo99

Original post by theslav

E=hv v is the frequency of light transmitted so if red light is transmitted then frequency is lower so E decreases

it said the colour of the solution was red. this means red light photons were not absorbed by the electron... instead blue light photons(at the opposite end of the spectrum) were absorbed by the electron while red light frequences were remitted/ passed through :smile:

Reply 2915

TLi1295

Original post by MrMeep2580

For the first one of the enthalpy of lattice formation and the perfect ionic model did anyone put equal to?

Because AgCl. Ag is a large atom so it can't distort the Cl- orbital to cause covalent character I thought but I dunno

This was posted from The Student Room's iPhone/iPad App

I put equal to...but I really wasn't sure if they wanted to know about the tiny difference in values...because obviously there would be a small amount of polarisation but AgCl is supposed to be largely ionic isn't it? It's not like Al2O3? I don't know :/

Posted from TSR Mobile

Reply 2916

mulac1

ok - well the next question I remember best is Q7 the ions one...

7) original colours, final observation, equation for each reaction

a) [Fe(H2O)6]2+ and [Fe(H2O)6]3+ with sodium carbonate (I think this was 5 marks)
b) [Cu(H2O)6]2+ and [Co(H2O)6]2+ with HCL (4 marks)
c) [Cr(H2O)6]3+ and [Fe(H2O)6]2+ with excess OH (4 marks)
d) [Al(H2O)6]3+ and [Ag(H2O)2]+ with excess NH3 (4 marks)

Reply 2917

cuckoo99

Original post by PhoenixSeeker

Did you put colourless going to colourless?

i put initial : colourless
final observation : no observable change

Reply 2918

mulac1

lets try Q8 now - I'm going to need some help...

8a) ethanal can be oxidised to ethanoic acid by O2. Explain why Co2+ ions can increase the rate of this oxidation. Write 2 equations showing how Co2+ does this. (4 marks)

b) [X(H2O)6] reacts with an excess of ethane-1,2-diamine. Write an equation for this reaction and explain why ethane-1,2-diamine is the more stable complex (3 marks)

c) Draw the complex ion. (3 marks)

d) Cobalt ratio question (5 marks)

(edited 10 years ago)

Reply 2919

username890104

Original post by theslav

E=hv v is the frequency of light transmitted so if red light is transmitted then frequency is lower so E decreases

The 'v' in the equation is the frequency of the light absorbed. This being blue light, as the solution was red, and the complementary colour to that transmitted is absorbed.

As v is higher for blue light, and v is proportional to ΔE, then it was an increase.