This discussion is now closed.

Check out other Related discussions

OCR B (Salters) Chemistry F331 (Chemistry for Life) Thursday 23rd May Exam Discussion

Scroll to see replies

Reply 200

nick d terrier

Original post by CoolRunner

1 mark? I think.

yehh 1

Reply 201

krisshP

What everyone say for the question on why there's a smaller peak at m/z 20? I threw in molecular fragmentation of water, is this right?

Water Mr=18, so it makes sense to get peaks below18 which are smaller, but HOW do you get peaks above 18?

Reply 202

DomGunstone

Original post by krisshP

What everyone say foe the question on why there's a smaller peak at m/z 20?
I threw in molecular fragmentation of water.

Yeah, I also put this.

I saw fragmentation in one of the past papers, so we should be fine :smile:

Reply 203

emicroteen96

i said fragmentation as well

Reply 204

krisshP

Original post by emicroteen96

i said fragmentation as well

Original post by DomGunstone

Yeah, I also put this.

I saw fragmentation in one of the past papers, so we should be fine :smile:

Water Mr=18, so it makes sense to get peaks below18 which are smaller, but HOW do you get peaks above 18?

Reply 205

Ikklemini

Original post by krisshP

1 HF-->50%-->6000 years
2HF-->25%-->12,000 years
3HF-->12.5%-->18,000 years

They told you the HF was 6000 years

Oh fugggerr!! I did 12000 x 2 instead of 12000 add 6000 ffss lol stupid mistake

Reply 206

krisshP

Makes no sense to get peaks above 18

Reply 207

Ikklemini

Original post by krisshP

Water Mr=18, so it makes sense to get peaks below18 which are smaller, but HOW do you get peaks above 18?

If u use an isotope of O with a mass off 18, it would add up to 20 including the hydrogen atoms in the water molecule

Reply 208

emicroteen96

youre right the highest one is usually the compound, but its 18 not 20

Reply 209

krisshP

Original post by Ikklemini

If u use an isotope of O with a mass off 18, it would add up to 20 including the hydrogen atoms in the water molecule

So then fragmentation of water is wrong right?

Reply 210

nukethemaly

How many UMS is this paper out of?

Reply 211

DomGunstone

Original post by krisshP

So then fragmentation of water is wrong right?

It's right.

You could just say that 2 or more electrons have been removed from the outer shell/s as an alternative answer.

Reply 212

Kathiye

For the one where we had to write an ion, was it 18/6 O (-2)?

Reply 213

DomGunstone

Original post by nukethemaly

How many UMS is this paper out of?

90 UMS

Reply 214

krisshP

Original post by DomGunstone

It's right.

You could just say that 2 or more electrons have been removed from the outer shell/s as an alternative answer.

No you can't since then the charge would be say +2 nd m/z where z=+2 would mean a lower peak, not a greater peak at m/z 20 they were asking for

Reply 215

SyedaK

How do you convert results to UMS?

Posted from TSR Mobile

Reply 216

Ikklemini

Original post by krisshP

So then fragmentation of water is wrong right?

Fragmentation would have a m/z lower than 20 and it said in thhe question many isotopes of oxygen with the MAIN one being 16-O

Reply 217

RevisionEssence

Original post by krisshP

One question was about writing a reaction. It was worth only 1 mark and it did NOT mention anything on state symbols. I wrote the reaction, but didn't put state symbols since I was a bit unsure with what the state symbols would be or that reaction and I didn't want to risk showing incorrect state symbols. Is this okay?

There was only one where it asked about state symbols, lets just hope the one you're describing isnt it. :P

Reply 218

DomGunstone

Original post by SyedaK

How do you convert results to UMS?

Posted from TSR Mobile

http://www.ocr.org.uk/i-want-to/do/check-results/interpreting-results/

Reply 219

jehearo

Original post by madrevision

what error, i got the ion question wrong- on the back page

At first I didn't notice that they were talking about water but then four minutes to the end I finally noticed and quickly wrote down the right answer *phew*

Posted from TSR Mobile