OCR Chemistry F322 June 2016

Original post by nicoleemmak

Would you not have done moles of the other thing x125 then worked out the mass from that

That's what I'm saying!! What was your final mass you got 0.3 something right?? :smile:

)

Reply 81

nicoleemmak

What did everyone write for the one about adding acid and alkali to shift the equilibrium??

Reply 82

bakedbeans247

Original post by SlippyDuck117

I'm pretty sure I've seen this in a mark scheme, so 2/3 I'd say for sure.

Original post by mattyk5

yh i think you lose one mark for the "+"

Thanks. What about the enthalpy change question, working out Hr, i knew i should have included the mass of magnesium as well, plus i didn't put the minus sign in the answer! how marks out of 4 do you think?

Reply 83

nicoleemmak

Original post by mercuryman

That's what I'm saying!! What was your final mass you got 0.3 something right?? :smile:

)

I can't remember but probably If we did it the same way :smile:

Reply 84

hollygc123

7

Did anyone get something like 0.38 for the mass of mg? because m=0.0125x24.3 =0.303. And then you multiply that by 1.25 to add the 25% which gave 0.379 so 0.38 to 2dp??

Reply 85

sa32rra

Original post by mercuryman

That's what I'm saying!! What was your final mass you got 0.3 something right?? :smile:

)

0.38 is what i got :smile:

Reply 86

mattyk5

Original post by nicoleemmak

What did everyone write for the one about adding acid and alkali to shift the equilibrium??

acid shifts to the right because increase H+ conc
alkali shifts to the left because decreases H+ conc and increases (OH from water)

But i think for the alkali i shouldve wrote about it JUST decreasing the H+ conc so the equilbruim moves to ITS side. idk why i mentioned water etc

Reply 87

sa32rra

1062 for the bond enthalpy of CO?

Reply 88

SlippyDuck117

Original post by bakedbeans247

Thanks. What about the enthalpy change question, working out Hr, i knew i should have included the mass of magnesium as well, plus i didn't put the minus sign in the answer! how marks out of 4 do you think?

Although it varies from paper to paper, I've seen these sort of statements in mark schemes:
1 mark for bonds broken, calculated correctly
1 mark for bonds formed, calculated correctly
1 mark for correct Hr
1 mark for the correct sign

So at least 1, probably 2 marks. Unless I'm thinking about the wrong enthalpy change question haha

(edited 7 years ago)

Reply 89

cyborgom

Original post by nicoleemmak

What did everyone write for the one about adding acid and alkali to shift the equilibrium??

i wrote when acid added dere is an increase in conc. of h+ dere to minimise dis change equilibrium shifts right or and for alkali oh- increases therefore left

Reply 90

bakedbeans247

Original post by SlippyDuck117

Although it varies from paper to paper, I've seen these sort of statements in mark schemes:
1 mark for bonds broken, calculated correctly
1 mark for bonds formed, calculated correctly
1 mark for correct Hr
1 mark for the correct sign

thnks, what do you think the grade boundaries will be like? Also how many marks was the last question?

Reply 91

SlippyDuck117

Original post by bakedbeans247

thnks, what do you think the grade boundaries will be like? Also how many marks was the last question?

I'm pretty sure the last question was 13 marks.

I'm not sure about what the grade boundaries will be. Personally I reckon about 79-82 for an A, however that might be affected by the nature of the exam, i.e. only resit candidates took it.

What does everyone else reckon an A would be?

Reply 92

cyborgom

Original post by Pingu7

That's what I got because they gave enthalpy of combustion values in the table provided

what did u guys got for bond enthalpy one?

Reply 93

BrownGuyIrfan

Original post by mercuryman

You work out the molecular formula straight away which was c3h7br , I'm pretty sure that's what I got

0.38 should be correct, got that as well. Also for the mr I got 122.9 or something like that

Reply 94

IronMind

I somehow got 30.8 grams for the magnesium.. somebody explain?

Reply 95

mercuryman

Original post by SlippyDuck117

I'm pretty sure the last question was 13 marks.

I'm not sure about what the grade boundaries will be. Personally I reckon about 79-82 for an A, however that might be affected by the nature of the exam, i.e. only resit candidates took it.

What does everyone else reckon an A would be?

86/100 for an A

100/100 for max

Therefore, losing around 9-10 marks would score you around 137 ums/150 ums
Which in my opinion is decent

Reply 96

bakedbeans247

Original post by SlippyDuck117

I'm pretty sure the last question was 13 marks.

I'm not sure about what the grade boundaries will be. Personally I reckon about 79-82 for an A, however that might be affected by the nature of the exam, i.e. only resit candidates took it.

What does everyone else reckon an A would be?

Oh my! I totally forgot that bec it's only re-sitters it'll increase the grade boundaries, plus that paper was pretty is no? Daam...all i needed was a strong B and i flopped by running out of time and making silly mistakes.

Reply 97

nicoleemmak

Original post by SlippyDuck117

I'm pretty sure the last question was 13 marks.

I'm not sure about what the grade boundaries will be. Personally I reckon about 79-82 for an A, however that might be affected by the nature of the exam, i.e. only resit candidates took it.

What does everyone else reckon an A would be?

An a definitely won't be higher than 84 but could be anything between 75-84. The highest they've ever been were 83 in Jan 2012- but remember that was only retakers too.
Don't freak out about it only being retakers because every Janurary f322 was only retakers aswell

(edited 7 years ago)

Reply 98

Derek12353

Original post by nicoleemmak

Would you not have done moles of the other thing x125 then worked out the mass from that

Yes that is how you calculate it

Reply 99

SlippyDuck117