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B (Salters) F331 (Chemistry for Life) 22nd May 2015 [Official Thread]

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Original post by shooting_stars
They asked for silicate (which means it has oxygen) not silicon ion.. I did the same mistake


Oh dear :frown:
Reply 101
Avatar for Eddyamz
Eddyamz
-196?
Original post by shooting_stars
That's the same thing I did... I didnt realise they asked for silicate not slicon one


Great, that's already like 10 marks down the drain. There goes my A

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Original post by DominoMatrix227
Who else got 278 for the volume of the gas?


Me!
Original post by shooting_stars
They asked for silicate (which means it has oxygen) not silicon ion.. I did the same mistake


Yep. It asked for silicate. Don't worry plenty of people made that mistake as well.
(SiO3)2- is probably the right answer. Messed it up and only realised after.
Can we get an Unofficial Mark scheme going?
Original post by HecTic_H
Can we get an Unofficial Mark scheme going?


Yes please.

Posted from TSR Mobile
yeah no deff got the last one wrong... dropped a few marks for sure

not to sure about the Hr decomposition enthalpy question!
any help?
Question 2 enthalpy calculation? What did you guys get?
Original post by Kichelle
Question 2 enthalpy calculation? What did you guys get?


+196

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Reply 110
Avatar for Eddyamz
Eddyamz
-196 or +196 for enthalpy change question?
Original post by Eddyamz
-196 or +196 for enthalpy change question?


+ because it was formation, had to redo that question many times

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Original post by Eddyamz
-196 or +196 for enthalpy change question?


i got -196 because it was +376-572= -196
Reply 113
Avatar for zvhra
zvhra
5
Original post by TheGreatImposter
+ because it was formation, had to redo that question many times

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It was decomposition of hydrogen peroxide, not formation


Posted from TSR Mobile
Original post by TheGreatImposter
+ because it was formation, had to redo that question many times

Posted from TSR Mobile


But i have seen questions where formation is exothermic sometimes.. I drew the Hess's cycle and both were minus values but then the first value you had to change it to a + because you had the change the arrow to make the Hess's cycle work..
For the electron energy question (5 marks), my answer was:

Energy lost as electrons drop from higher to lower energy levels
E = hv
This gives a specific line
Energy gaps specific for each element
Diagram.

Did anyone else get these points?
Original post by DominoMatrix227
For the electron energy question (5 marks), my answer was:

Energy lost as electrons drop from higher to lower energy levels
E = hv
This gives a specific line
Energy gaps specific for each element
Diagram.

Did anyone else get these points?


Did the exact same :smile:
Original post by shooting_stars
But i have seen questions where formation is exothermic sometimes.. I drew the Hess's cycle and both were minus values but then the first value you had to change it to a + because you had the change the arrow to make the Hess's cycle work..


But part 2 confirmed that the reaction produced heat so it had to be exothermic, so I put my value as negative (can't remember what it was)
I put 109 for the bond angle, but did it ask for the expected or actual bond angle?
Was the actual bond angle greater or smaller than the predicted?

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