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OCR Chemistry F322~ 4th June 2013~ AS Chemistry

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Original post by Dejir
What is heterogeneous catalyst


A catalyst that doesn't change it's state? :/
Hey I'm a little stuck on mass spec, on a mark scheme it says that an m/z of 45 indicates the loss of a ch3, but how do you know this??? So confused :frown:


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Original post by Dejir
What is heterogeneous catalyst


A catalyst in a different phase to the reactants.
Original post by KatiexZoe
Hey I'm a little stuck on mass spec, on a mark scheme it says that an m/z of 45 indicates the loss of a ch3, but how do you know this??? So confused :frown:


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45 doeesn't correspond to ch3. ch3 has an m/z value of 15. 45 is most likely CH2CH2OH+
Reply 2484
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FLLF
Original post by KatiexZoe
Hey I'm a little stuck on mass spec, on a mark scheme it says that an m/z of 45 indicates the loss of a ch3, but how do you know this??? So confused :frown:


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The Mr of the compound is 60 (from rightmost peak), so an m/z value of 45 indicates the loss of something with an Mr of 15, which is CH3
Do we need to know what the states of organic compunds in different reactions are? I know I'm being vague, but is there any specific ones we HAVE to know?
Original post by rollinglikerob
Do we need to know what the states of organic compunds in different reactions are? I know I'm being vague, but is there any specific ones we HAVE to know?


Yes, h2o is a gas in the hydration of alkenes to form alcohols. :wink:
Reply 2487
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wndms
1
Can someone answer this for me?
In Q=mcdeltaT question, if the temperature is endothermic, so like temperature fell from 30'C to 20'C, is the value of T = -10 or +10?

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Original post by wndms
Can someone answer this for me?
In Q=mcdeltaT question, if the temperature is endothermic, so like temperature fell from 30'C to 20'C, is the value of T = -10 or +10?

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T = 10.
Original post by wndms
Can someone answer this for me?
In Q=mcdeltaT question, if the temperature is endothermic, so like temperature fell from 30'C to 20'C, is the value of T = -10 or +10?

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Temperature fell, so -10


Original post by GeneralOJB
Yes, h2o is a gas in the hydration of alkenes to form alcohols. :wink:


Thanks, are there any others?
Reply 2490
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FLLF
Original post by wndms
Can someone answer this for me?
In Q=mcdeltaT question, if the temperature is endothermic, so like temperature fell from 30'C to 20'C, is the value of T = -10 or +10?

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Delta something is always positive. If the reaction is exothermic, just remember to put a minus sign before your answer to the enthalpy change.
Reply 2491
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FLLF
http://www.ocr.org.uk/Images/131287-question-paper-unit-f322-chains-energy-and-resources.pdf

Can somebody explain 2b vi?
I don't understand how we are meant to know what the structure of the compound is...
Original post by rollinglikerob
Temperature fell, so -10




Thanks, are there any others?


Bro, that's just wrong. If the temperature fell, then energy has been used, meaning it is endothermic and the sign on the delta H will be positive.
Original post by FLLF
http://www.ocr.org.uk/Images/131287-question-paper-unit-f322-chains-energy-and-resources.pdf

Can somebody explain 2b vi?
I don't understand how we are meant to know what the structure of the compound is...


Go back and look at the mechanism, but replace the water molecule with ethanol. All should become clear.
Reply 2494
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liam627
actually feel really prepared for this exam.
Reply 2495
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iamvick
2
GeneralOJB you're on fire this morning!!

Haha awesome stuff.
Reply 2496
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FLLF
Original post by GeneralOJB
Go back and look at the mechanism, but replace the water molecule with ethanol. All should become clear.


Do you replace the water with CH3O instead of CH3OH, because one of the Hydrogens is used in step 1? Thanks for your help btw
Original post by FLLF
Do you replace the water with CH3O instead of CH3OH, because one of the Hydrogens is used in step 1? Thanks for your help btw


Nope, CH3OH - that's what it's reacting with. :smile:
Reply 2498
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d.adrian
Original post by SheriB
Its okay someone put it up. thanks anyway


np
Original post by GeneralOJB
Bro, that's just wrong. If the temperature fell, then energy has been used, meaning it is endothermic and the sign on the delta H will be positive.


Q=mcDeltaT is the absorbed by or lost from the surroundings. Temperature has been lost, so -10 in the equation, gives you a negative value, so the energy absorbed by or lost from the chemical system is simply Q with the opposite sign. From there you can work out the enthalpy change per mole

EDIT: that sounds confusing as ****. In this case Q is negative because the surroundings have lost energy, and chemical system has gained energy. So Q=-whatever, and DeltaH of reaction is +
(edited 10 years ago)

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