Year 12s: what will be the first way you research your future options? >>

OCR B Salters - F335 Exam - 15 June 2011

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Reply 620

beckyxo

Original post by brendan.

I put...

The benefits of the herbicide outweigh the risks.

There could be more stringent measures involved to prevent the herbicide getting close to humans or other mammals.

ohh! i see! :smile:

Reply 621

francescaxxx

SF6 was one and LiF I think!
I put covalent for SF6 and ionic for the other.

I was so confused be the conjugate acid question!!! Damn it ! Now I know the answer it seems so obvious!!

Reply 622

tom108

Original post by 04ayasin

I think I did well. I see a lot of people saying they found it hard. Good luck to everyone. I attempted all the questions a few people i know ran out of time. some people didn't learn the reactions so they got stuck on them.

I didnt get the question where you had to ring the bit on the molecule that went into the plant cell or something. Ringed the benzene ring. I also didn't get the oxidation state for sulfur, so I guessed that as well can't remember what I put.
For the hexaflouride question I guessed the following:
2SF4 + O2 --> SF6 + SO2 + F2
What did others put?

Thats wrong i think sorry. :/

3SF2 + 02 ---> 2SF6 + SO2

Reply 623

04ayasin

Original post by ManPowa

H3Po4

Metallic bonding.. Lithium is a metal right?
And what were the other two?

Noooo

I put H3PO4 but changed it for some reason to NaH2PO4, I didn't know what conjugate meant.

I got metallic bonding for lithium as well

Reply 624

tom108

Original post by francescaxxx

SF6 was one and LiF I think!
I put covalent for SF6 and ionic for the other.

I was so confused be the conjugate acid question!!! Damn it ! Now I know the answer it seems so obvious!!

Whatsthe conjugated acid ?

Reply 625

04ayasin

Original post by tom108

Thats wrong i think sorry. :/

3SF2 + 02 ---> 2SF6 + SO2

Oh well I was close I guessed that SO2 was produced correctly. Might manage to get a mark.

Reply 626

francescaxxx

Whats the conjugate acid of H2PO4 ^-? Was the question i was on about - apparently the answer is H3PO4 :frown:

Missed that!

Reply 627

ManPowa

Original post by tom108

Whatsthe conjugated acid ?

H3Po4.. Saw it in a previous exam off the legacy spec

Reply 628

tom108

Dam i knew that :frown:

Reply 629

zahre

Original post by francescaxxx

SF6 was one and LiF I think!
I put covalent for SF6 and ionic for the other.

I was so confused be the conjugate acid question!!! Damn it ! Now I know the answer it seems so obvious!!

I put simple molecular for this. :redface:

Reply 630

francescaxxx

Original post by zahre

I put simple molecular for this. :redface:

Yeah that makes more sense! The longer I stay on here the more marks I realise I have lost ! Oh well.. not much i can do now!

Reply 631

meerar20

Original post by SmileyGurl13

I'm so confused :s-smilie:

I still think it's 19!! xD

Yeahh, I got 19.4g (:

Reply 632

04ayasin

Also what did people to for the mass of the salt or acid cant remember which it asked, think it asked for the salt. I did:

Ka= [H+] x [acid]/[salt]

I used pH to find [H+] Ka was given and so was [salt or acid] I then rearanged it.
Used moles = conc x vol
then mass = moles x Mr

Reply 633

AFK

Original post by brendan.

I put...

The benefits of the herbicide outweigh the risks.

There could be more stringent measures involved to prevent the herbicide getting close to humans or other mammals.

I said that there would be an increase in the yield of crops. Also said lower concentrations will be used therefore it won't be that harmful to humans or animals ( Said in the question that the herbicide causes the plants to grow too quickly).

Not sure if its right though :s-smilie:

Reply 634

tom108

Anyone have the answers have Lithium (i) sulphie ???????

Reply 635

rhiannonroyalle

Fml. I feel like OCR just hadouken'd the hell out of me. Here's to reapplying to med school next year, facing £9000 fees, and resits.

Reply 636

twelve

Original post by Tetanus

What did everyone get for the mass? I got 12g.

I got it through n = V x C / 1000 then n = m / Mr??

Oh no, I think I got this wrong...

You mean the one about how much was dissolved to make the buffer?

I think this is what I did. It was pH 7, so I worked out the concentration of H+ needed, then substituted that into the equation for Ka, and found what the ratio of the other two was. Then substituted in the concentration that we were given to find the concentration of the other one. Then converted that concentration into g dm-3 and got something like 19 g?

Thinking back I don't think that was right, but it completely made sense at the time haha.

Some really nasty questions on that paper, but some nice ones too :smile:

I'm now going to unsubscribe to this thread so I don't realise any others I've got wrong and start panicking haha.