OCR A2 Chemistry: Unifying Concepts June 2008

W41337

Why would NH3 be of benefit to the farmer??? it's toxic :s-smilie:

Fertilizer?

Reply 41

mitz

W41337

Why would NH3 be of benefit to the farmer??? it's toxic :s-smilie:

not to plants

Reply 42

Candescence

bongo fury

Yeah i originally doubled the no. of moles, because it seemed like 2 moles of whatever it was formed from 1 mole of limestone. But then i changed it because it was just that in the second equation eveything had been multiplied by 2

That's what i did presumably. How i didn't realise that 1 calcium atom can't produce 2 calcium atoms i don't know lol

Reply 43

*The One

W41337

Why would NH3 be of benefit to the farmer??? it's toxic :s-smilie:

Although this is biology nitrifying bacteria like nitrobacter or nitrosomonas convert into into nitrates which are taken up be the crops and used to synthesise amnio acids? SO bascially chemistry standard answer is increases crop yield?

Reply 44

Sky Twilight

W41337

Did anyone get that lol???

I think I put that down :s-smilie:

But it said ionic bonding.. and I'm not sure why, but I looked up Nitrogen and it was in group 5..?

Reply 45

Sky Twilight

But it said ionic bonding..

Did it? I just assumed...C and N are both non-metals so covalent :s-smilie:

Reply 46

nexttime

22

i put carbonic acid for that question; i worked out the pH with 0.2M and it was in the range, whereas all others were out.

Reply 47

nexttime

22

cptbigt

Did it? I just assumed...C and N are both non-metals so covalent :s-smilie:

it was covalent i'm sure. it said draw the bonding within this ion, nothing about ionic bonding i think :s-smilie:

Reply 48

Andy Conda

2

cptbigt

Did it? I just assumed...C and N are both non-metals so covalent :s-smilie:

Yeh, It said ionic bonding, so I got confused :confused:

Reply 49

W41337

No it said CaCN2 was ionic in that there is ionic interaction between teh Ca2+ ion and the CN2- ion. The structure of CN2- is not ionic as it is two non-metals

Reply 50

mc999

wat did every1 put for the last question like the equations and benefits?
Did anyone get the reason y u picked a acid given from the table for a buffer solution?
Anyone know wat the answer was for tht mole fraction?

Reply 51

mc999

wat did every1 put for the last question like the equations and benefits?
Did anyone get the reason y u picked a acid given from the table for a buffer solution?
Anyone know wat the answer was for tht mole fraction?

I put methanoic acid...it had a pKa in the range of the given pH.

Reply 52

username138327

Pretty alrite. Probably an comfy A. Me = happy.

Reply 53

The man called Fellas

Pretty alrite. Probably an comfy A. Me = happy.

Hah lucky you. I got 60/60 for my c/w, but doubt I got much more then 10 on that exam....

Reply 54

bongo fury

For the last question about producing a flame, did anyone else just put a reaction with oxygen to make carbon dioxide and water, and then balance it?

Reply 55

bongo fury

For the last question about producing a flame, did anyone else just put a reaction with oxygen to make carbon dioxide and water, and then balance it?

Yeah combustion..

C2H4 + 2.5O2 -> 2CO2 + H2O

Reply 56

Andy Conda

2

bongo fury

For the last question about producing a flame, did anyone else just put a reaction with oxygen to make carbon dioxide and water, and then balance it?

Yep

For the hydrolysis part, will you get a mark for putting H20 in equation. It was 4marks!

Reply 57

trickz

10

That's what I did but then I changed it and put the C2H4+O2 ---> C2H4O2 :s-smilie:

Reply 58

username138327

cptbigt

Hah lucky you. I got 60/60 for my c/w, but doubt I got much more then 10 on that exam....

Thanks. The calculations will pull me through I think. Is that possible to do so well in C/w and then so bad on the exam, or are you like my friend who panics and thinks they've done bad but still get A's all the time :wink:

Reply 59

*The One