AQA CHEM5 A2 Chemistry - 19th June 2013

Reply 2940

Anshul91

there was a question on hydration of why cl- has a higher hydration than br- i think

Reply 2941

Anshul91

there was also a question on why SiO2 has a higher BP then P4o10

Reply 2942

Xiomara

18

There was also a question which required you to draw the boiling point of a substance on a graph.

Reliable grade boundary predictions, anyone? Easier or harder than Jan13? Reckon I've lost anywhere from 13 to 17 marks, depending on how lenient they want to be...bye bye A*, haha.

EDIT - I remember a define lattice enthalpy of disassociation, and explain perfect ionic model questions.

(edited 10 years ago)

Reply 2943

Anshul91

you know the enthalpy of solution question they gave the hydration of one species was the hydration of the other the same?

Reply 2944

mulac1

lets do the periodicity question ... I think it was number 4 (?)

a) What is the bonding in MgO. How could you prove that MgO has this bonding (3)
b) What is the bonding in SiO2 and why does it have a high melting point (3?)
c) What has a higher melting point - SiO2 or P4O10? Explain (3)
d) Write an equation to show that MgO is basic (1)
e) Write an equation for the reaction of P4O10 with MgO (1)

Reply 2945

mulac1

right - just Q2 and Q3 left now ... I think 2 was the solution stuff and I think 3 was the entropy stuff.. I cannot really remember these questions..
Q2) why is the hydration enthalpy of the Cl- ion larger than that of the Br- ion? (2 or 3)
calculate the enthalpy of solution for KBr (2)
the enthalpy change for this reaction is +17.3 (?), explain why the dissolution of KBr is feasible above x degrees (?)
I think thats nearly all I can remember...

(edited 10 years ago)

Reply 2946

Anshul91

what was that enthalpy of solution question we did, they didn't give us one value for the hydration and asked for the dissociation i think??

Reply 2947

nimbusquaffle

for ΔE=hv question

v=ΔE/h

using a greater ΔE, v would be greater: 2x10^-3/6x10^-34=3x10^30
makes a greater (v) frequency --> blue colour

therefore a decrease in ΔE would lead to a smaller frequency --> red frequency

am I right? I hope so :smile:

Reply 2948

reakhy

Original post by mulac1

right - just Q2 and Q3 left now ... I think 2 was the solution stuff and I think 3 was the entropy stuff.. I cannot really remember these questions..
Q2) why is the hydration enthalpy of the Cl- ion larger than that of the Br- ion? (2 or 3)
I think thats nearly all I can remember...

All I remember of 2,
2a) Why is hydration enthalpy larger for Br- than CL-? (3)
2b) Calculate Enthalpy of Solution for KBr (3)

Reply 2949

Joshalos

15

Original post by mulac1

lets do the periodicity question ... I think it was number 4 (?)

a) What is the bonding in MgO. How could you prove that MgO has this bonding (3)
b) What is the bonding in SiO2 and why does it have a high melting point (3?)
c) What has a higher melting point - SiO2 or P4O10? Explain (3)
d) Write an equation to show that MgO is basic (1)
e) Write an equation for the reaction of P4O10 with MgO (1)

a) Ionic. Heat until molten. If it conducts electricity it is ionic.

b) Covalent. Macromolecule (giant covalent structure). Strong covalent bonds require a lot of energy to break.

c) SiO2 - Has strong covalent bonds between molecules whereas P4O10 has weak van der Waal between molecules which require little energy to break.

d) MgO + 2HCl --> MgCl2 + H20

e) Wasn't this a reaction with NaOH? If so P4O10 + 12NaOH ---> 4 Na3PO4 + 6H2O

(edited 10 years ago)

Reply 2950

mulac1

entropy Q:
why is deltaS 0 at 0K? (2)
Why does the line slope up at the start of the graph? (2)
Mark on the appropriate axis the boiling point of the substance (1)
Why is change L2 bigger than change L1 (2)

how does this graph resemble y=mx + c (2)
what happens below temperatures of 500K (2?)

Reply 2951

mulac1

Original post by Joshalos

a) Ionic. Heat until molten. If it conducts electricity it is ionic.

b) Covalent. Macromolecule (giant covalent structure). Strong covalent bonds require a lot of energy to break.

c) SiO2 - Has strong covalent bonds between molecules whereas P4O10 has weak van der Waal between molecules which require little energy to break.

d) MgO + 2HCl --> MgCl2 + H20

e) Wasn't this a reaction with NaOH? If so P4O10 + 12NaOH ---> 4 Na3PO4 + 12H2O

it was sorry :smile:

Try and help me get the questions to Q2 and 3 please :smile:

Reply 2952

Xiomara

18

Original post by Joshalos

a) Ionic. Heat until molten. If it conducts electricity it is ionic.

b) Covalent. Macromolecule (giant covalent structure). Strong covalent bonds require a lot of energy to break.

c) SiO2 - Has strong covalent bonds between molecules whereas P4O10 has weak van der Waal between molecules which require little energy to break.

d) MgO + 2HCl --> MgCl2 + H20

e) Wasn't this a reaction with NaOH? If so P4O10 + 12NaOH ---> 4 Na3PO4 + 12H2O

Isn't it 6H2O?

Reply 2953

mulac1

Original post by Xiomara

Isn't it 6H2O?

before we start giving answers can we please try and get all the questions...

Reply 2954

Muppet Science

14

Original post by Xiomara

Isn't it 6H2O?

Yup

Reply 2955

teen1234

Original post by mulac1

entropy Q:
why is deltaS 0 at 0K? (2)
Why does the line slope up at the start of the graph? (2)
Mark on the appropriate axis the boiling point of the substance (1)
Why is change L2 bigger than change L1 (2)

how does this graph resemble y=mx + c (2)
what happens below temperatures of 500K (2?)

a. Highest state of order, no vibration
b. As T increases, more kinetic energy, more vibration, greater disorder, higher entropy
c. Below L2
d. From liquid to gas at L2, larger change in entropy
e. easy
f. ( 1 mark) becomes feasable

Reply 2956

Joshalos

15

Original post by Xiomara

Isn't it 6H2O?

Woops, sorry, of course it is - rest assured I put 6H20 in my paper, I was just doing that quickly without thinking - I'll edit it now. :smile:

Reply 2957

mulac1

oh yes ofc how could we forget... calculate the temp when KBr is dissolved in water at 298K (5 marks)

Reply 2958

Joshalos

15

Original post by mulac1

oh yes ofc how could we forget... calculate the temp when KBr is dissolved in water at 298K (5 marks)

5g of KBr is dissolved in 20g of Water at 298K.

Reply 2959

Lizzie232

11

Original post by 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?

Yeah definitely, june grade boundaries are normally slightly lower than Jan at about 73 to get an A, you should be fine :smile:

AQA CHEM5 A2 Chemistry - 19th June 2013

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