Does anyone think I'll get a mark for the energy density Q? It was supposed to be near to 30000 or 36000 or something but then I divided this by 1000 so I got 36.something idk

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I'm sure you will get working marks but because the units were in Kjmol-1 I'm not sure about the final answer

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Reply 144

Daribig

Original post by Kira Yagami

for the Kno3, 74% is Kno3 right

so isn't it just 74/mr of kno3?

it was 2 marks

Wasnt it 3 marks?

Reply 145

sam2222

Ok i will make a list questions and answers I remember:

1. What does heterogeneous and catalyst mean (2)
-Catalyst and reactants are at different physical state. Catalyst speeds up the rate of reaction and can be recovered chemically unchanged at the end of the reaction
2. Write equation for reaction Mg + water (2)
- Mg(s) + 2H2O(l) ---> Mg(OH)2 (aq) + H2(g)
3. what is octane number in fuel (2)
- measure of the fuels tendency to auto ignite , the higher the more efficient the fuel
4. Explain how emission spectra are formed (4)..
- Electrons drop to lower energy levels
- emit light/photon
- energy level proportional to freq , e=hv

5. explain why spectra can be used to identify different element in fire works (1 or 2 marks)
- gaps between energy levels are unique for a given element
6. Explain the bond angle in Sio4 (3)
- 4 regions of electron density around the central S atom
- electrons repel to get as far as away as possible/minimize repulsion
- bond angle 109....(I think i put that or did I put 120, hopefully not )
7. What is the other product of reforming (1)
- H2
8. Explain hess law ( 3 or 4)
- the enthalpy change of a reaction is the same independent of the route taken, providing the stat and finish conditions are the same
9. Describe similarities or difference between atomic absorption and emission spectra ( 2 or 4 )
- Difference: atomic emission is coloured lines on black background , absorption black lines on coloured backgrounds
- Similar: - line get closer at higher frequency for both, or I think I put both are line spectra...
10- explain why there is an increase in entropy in equation 2.1 and explain what entropy is (i think.. not sure this is from the mock or real paper)(3)
- entropy is measure of disorder. nor mumber of ways blah blah balh arrange particles
- more moles of gas on the right side so higher entropy/ gas has the highest entropy
11. write equation for cracking of decane to give 3 carbon alkene and something else (1 or 2)
C10H22 + C3H..........

well you can fix and add to it...

(edited 7 years ago)

Reply 146

Kaz_96

Original post by Kwaks

Yeah, I think so... What did you get as the final answer???

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I got 34.15

Reply 147

username1084917

For the polstrene cup one,

The cup is a better insulator of heat so less heat loss to the surroundings from the solution right?

Reply 148

JgR1997

I remember a lot of the questions but I won't know the exact answers so i can supply the questions and someone supply the correct answers?

Reply 149

Kwaks

Original post by Kira Yagami

for the Kno3, 74% is Kno3 right

so isn't it just 74/mr of kno3?

it was 2 marks

So did you assume that that mass was 100g or?

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Reply 150

Kwaks

Original post by Kira Yagami

For the polstrene cup one,

The cup is a better insulator of heat so less heat loss to the surroundings from the solution right?

Yeeeeeeeep

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Reply 151

KINGYusuf

I wrote for similarity the position of the lines are in the same position for both? Is that right

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Reply 152

KINGYusuf

Upload the paper please!!!

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(edited 7 years ago)

Reply 153

username1084917

Original post by Kwaks

So did you assume that that mass was 100g or?

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I thought if 75% or whatever is Kno3 then 75/mr should give me the percentage of moles ? I dunno

Will i get alteast 1 mark?

Reply 154

Kwaks

Original post by KINGYusuf

I wrote for similarity the position of the lines are in the same position for both? Is that right

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Yep, If they are both spectra for the same element

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Reply 155

KINGYusuf

I got like 56% lol totally wrong

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Reply 156

sam2222

Original post by JgR1997

I remember a lot of the questions but I won't know the exact answers so i can supply the questions and someone supply the correct answers?

add to my list

Reply 157

username1084917

for the experiment ones

for one of them I put experiment not done in standard conditions

and for the other one I put evaporation of fuel/incompletel combustion