OCR Chemistry B Salters F331 May 22nd 2015

hi all,

What was everyone's overall impression of that paper?

I thought it was probably a bit on the harder side but that might just be kind of subjective for me, plus I'm not exactly an outstanding student.

Scroll to see replies

Reply 1

ZoeWoah

I think it was ok, emmision spectra was hard and so was the weird calculation about volume :frown:

what sign did you get for tbe enthalpy?

Reply 2

DelAccount123

-196 I think I got :smile:

Reply 3

Erica_Tsoi

Original post by Jonooo123

-196 I think I got :smile:

I've got the same then i've got
H2(g) + 1.5O2(g) -> H2O(l) + O2(g)

Reply 4

ayoush

That's what I got too, what did you get for the volume? I got 278.25 or something like that.

(edited 8 years ago)

Reply 5

Erica_Tsoi

Ive got
number of moles=mass/Mr= 90/(16+16+2)=2.65
2.65x70=185.3cm3
185/1000=0.185dm3 (converting cm3 to dm3)
Final answer= 0.185dm3
But not sure if it's right

Reply 6

DelAccount123

Original post by Erica_Tsoi

Ive got
number of moles=mass/Mr= 90/(16+16+2)=2.65
2.65x70=185.3cm3
185/1000=0.185dm3 (converting cm3 to dm3)
Final answer= 0.185dm3
But not sure if it's right

Wasn't the volume 70dm3 per mole?
I got moles of peroxide was 2.65 so moles of h20 was 2.65,moles of o2 was half of that so 1.325 number of moles of gas was 2.65+1.325, volume of gas was that number times 70 which came out as just under 288, anyone agree with this? :smile:

Reply 7

ks14

Yeah that's what I got :smile:

Reply 8

audreygal

Original post by Jonooo123

I got that.

Reply 9

KINGYusuf

For the equation I got 2H20 ----> O2 + 2H2 is that right? :redface:

For the volume is was like 277 or 278

Btw guys what did everyone get for the bond angle for C-C-C (according to repulsion theory & actual bond angle)

& what did everyone write down for the decomposition of Nitrogen Peroxide?

Reply 10

audreygal

Made so many stupid mistakes!!

Reply 11

audreygal

[QUOTE="KINGYusuf;56114311"]For the equation I got 2H20 ----> O2 + 2H2 is that right? :redface:

Reply 12

DelAccount123

Original post by KINGYusuf

For the equation I got 2H20 ----> O2 + 2H2 is that right? :redface:

Bond angle should be 109 in theory but cyclopropane is a a triangular shaped molecule so bond angle is less, towards 60 degrees! Also equation was for formation of water so 2H2 +O2 - - - > 2H2O

(edited 8 years ago)

Reply 13

Erica_Tsoi

Original post by KINGYusuf

For the equation I got 2H20 ----> O2 + 2H2 is that right? :redface:

H2(g) + 1.5O2(g) -> H2O(l) + O2(g)

109 Tetrahedral

N2O -> N2 +O (Not sure for this one)

Reply 14

KINGYusuf

Original post by Erica_Tsoi

H2(g) + 1.5O2(g) -> H2O(l) + O2(g)

109 Tetrahedral

N2O -> N2 +O (Not sure for this one)

Is my equation right also?

Reply 15

Erica_Tsoi

Original post by KINGYusuf

Is my equation right also?

Should be H2(g) + 1.5O2(g) -> H2O(l) + O2(g)

Reply 16

audreygal

Thought I could get 100 UMS😭😭

Reply 17

ayoush

Original post by KINGYusuf

For the equation I got 2H20 ----> O2 + 2H2 is that right? :redface:

My equation on the formation of water was the other way around, but i got that volume and i put 109 for the predicted bond angle and that it was actualy reduced. For the decomposition i put 2N2O--->2N2+O2