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

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Did we have to state what the actual bond angle was? Or just state whether it was greater or smaller?
Just use the graph, from best fit

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Original post by f.loco
Q1:
Mass of e: v.small
The others are basic

Ionisation
Acceleration
Drift region

Mass spec, same Ek given to each particle heavier reach later than lighter which is detected by detector and form mass spec graph


Left gaps so it fits the same patterns

Beta decay was Se + 2e

Vol of gas: 277.2/8

Ar of Ge: 72.7

Ion in end: SiO3^2-

Bonding is ionic

Cloudy as co2 forms precipitate

NO2 as high temp and pressyre by engine creates right conditions for O2 and N2 to form bonds

Reforming
Hydrogen


Purpose of catalyst to speed up reaction

2 variables: same mass of metals
Sams heating time

-196kJmol^-1

Bond angle: 109° but actual 104° as corners squeeze the electron clouds.

Emision spec: descrete E level, e- absorb photon. Excited to higher shell. When return to geound state release photon of characteristic frequency eqaual to E/h. Diff spec for diff elements as diff electron arrangement

Theres some answers i put down



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How did you work out the volume one?
I got 1.7, knowing my luck it'll be 2.0 +/- 0.2


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Original post by ZoeWoah
How did you work out the volume one?


1. Worked out the no of moles for all the compounds using n=m/Mr

Then used V=n x 70 for both gases

Then added the 2 volumes up (185.3484.. + 72.849..) which gave me 277.8 something

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(edited 8 years ago)
Original post by f.loco
1. Worked out the no of moles for all the compounds using n=m/Mr

Then used V=n x 70 for both gases

Then added the 2 volumes up (185.3484.. + 72.849..) which gave me 277.8 something

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I did the mr of hydrogen peroxide -.-
Reply 146
Avatar for Adam971
Adam971
For the mass spectrometer question, in the 2014 paper it wanted you to say KE=1/2mv^2 for 1 mark. It never asked for that in papers before 2014 so I wrote that just to be safe.
Original post by DominoMatrix227
How did everyone do that half life question? I took 3 values (all different) and took an average to get 2.0x10something.


Clever, I only did one half life haha
I think ill get about 52/54 or something
Any gueses on grade boundaries?
I think for an A it will be 50

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Original post by ZoeWoah
How did you work out the volume one?


Mol[H2O2] = (Mass)/(Mr) = ~2.something
Stoichiometric ratio = 2:3
* 70dm^3 = 278
Original post by ZoeWoah
I did the mr of hydrogen peroxide -.-


U do that first then compare ratios

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Original post by Shunder10
Mol[H2O2] = (Mass)/(Mr) = ~2.something
Stoichiometric ratio = 2:3
* 70dm^3 = 278

didnt do the ratio will i get a mark by finding out the mr of hydrogen peroxide and mutiplying by 70?
Original post by Adam971
For the mass spectrometer question, in the 2014 paper it wanted you to say KE=1/2mv^2 for 1 mark. It never asked for that in papers before 2014 so I wrote that just to be safe.


I wrote this after the point about accelerating to same Ek
How did people do the dot and cross diagram??
Mine was like
[Sr]2+ + [O]2-
with six dots and two crosses around the oxygen...
Original post by f.loco
1.8 for half life

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I got 1.8 as well!
Original post by ZoeWoah
didnt do the ratio will i get a mark by finding out the mr of hydrogen peroxide and mutiplying by 70?


You may

But youve found vol of H2O2 not the other gases

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Original post by Shunder10
How did people do the dot and cross diagram??
Mine was like
[Sr]2+ + [O]2-
with six dots and two crosses around the oxygen...


I did this, initially drew it as covalent but it clicked 1 min before the end of the exam, lucky I had enough time
Do you think the grade boundaries will be higher than last year???
Original post by f.loco
I think ill get about 52/54 or something
Any gueses on grade boundaries?
I think for an A it will be 50

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It was 45 for the june 2014 paper, and I'm sure that was easier
Original post by Shunder10
How did people do the dot and cross diagram??
Mine was like
[Sr]2+ + [O]2-
with six dots and two crosses around the oxygen...


I didnt put a plus sign in between the two, do i lose a mark, apsrt from that i got the other bits right

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