Official OCR AS Chemistry B (Salters) 27th May 2016 (new specification)

For the final calculation question about UVA's frequency and breaking a bond with enthalpy 320kJ/mol ( I think that's what it is), I'm pretty sure you're meant to calculate the frequency of energy required to break a bond with enthalpy of 320kJ/mol, and see if it's above or below the frequency of UVA. However, I did it the other way round and found the bond enthalpy that UVA is able to break... would I still get the marks, do you think?

Reply 21

Hariss

1

what molecule was non- polar in the multiple choice question?

Reply 22

katherine21678

Whatvdid you guys get for the Zn salt question at the beginning?

Reply 23

Jatman01

Original post by katherine21678

Whatvdid you guys get for the Zn salt question at the beginning?

I've that you need to filter it under reduced pressure and then heat the salt or use anhydrous salt

Reply 24

LaurenLovesMaths

14

Original post by Hariss

what molecule was non- polar in the multiple choice question?

I think I put BF3, as it's symmetrical so the dipoles cancel out?

Reply 25

LaurenLovesMaths

14

Original post by Jatman01

I've that you need to filter it under reduced pressure and then heat the salt or use anhydrous salt

yess! I put the same :biggrin:

Reply 26

LaurenLovesMaths

14

Is anyone able to put together an unofficial mark scheme by any chance? Thanks!

Reply 27

faxingstar

1

Original post by Dandie12

what about the last question for the number of molecules

It was the ideal gas equation pV=nRT where p is pressure in kelvins, V is volume in m^3 (so you had to convert cm^3 to m^3), n is number of moles, R is gas constant and T temp in kelvins. You had all the info except moles where you then divide this value by avagadros constant to get number of molecules.

Reply 28

Dandie12

1

Original post by Tommann1125

Did you have to leave the volume of chlorine produced calculation in standard form?

11000?

Reply 29

Shan_non

7

Original post by Hariss

what molecule was non- polar in the multiple choice question?

I put CH2CL2 because the dipoles cancel

Reply 30

Dandie12

1

Original post by Shan_non

I put CH2CL2 because the dipoles cancel

no they don't. chlorine is more electronegative

Reply 31

Tommann1125

Original post by Dandie12

11000?

Yeah I got that but was it meant to be like 1.1x10^4?

Reply 32

Dandie12

1

Original post by Tommann1125

Yeah I got that but was it meant to be like 1.1x10^4?

ah **** well then thats a mark dropped

Reply 33

faxingstar

1

Original post by Tommann1125

Yeah I got that but was it meant to be like 1.1x10^4?

11000 is 1.1x10^4

Reply 34

Dandie12

1

Original post by faxingstar

It was the ideal gas equation pV=nRT where p is pressure in kelvins, V is volume in m^3 (so you had to convert cm^3 to m^3), n is number of moles, R is gas constant and T temp in kelvins. You had all the info except moles where you then divide this value by avagadros constant to get number of molecules.

wouldn't you times by avagadro's constant?

Reply 35

faxingstar

1

Original post by Dandie12

wouldn't you times by avagadro's constant?

Yes, youre right I got that wrong. I feel like more time should have been given for that paper as i had to rush the last page in the final 10 minutes and then didnt get time to actually think and check my answers for mistakes. Did anyone else feel like this?

Reply 36

Dandie12

1

Original post by faxingstar

Yes, youre right I got that wrong. I feel like more time should have been given for that paper as i had to rush the last page in the final 10 minutes and then didnt get time to actually think and check my answers for mistakes. Did anyone else feel like this?