AS OCR chemistry B (SALTERS) F331 on the 15th may 2012

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Reply 380

ChloeTredinnick

Original post by TheStudent.

Yep bond angle of 109.

This question was stupid.
So would i get the marks for using them as two seprerate molecules

Reply 381

ells-13

Original post by Richyp22

Would you have got a mark for revewable?

If you stated it was from 'renewable energy' (wind power for example) you would get the mark but it is made from fossil fuels so not sure.

Reply 382

George_

Original post by AGrumpyMole

awesome! It took me about 10 mins, though :/

Yeah, I did it, panicked, stared at it till the end of the exam, and had to leave it as I'd done it, which was (we think) correct :P

It kept me entertained for the last 30 minutes :biggrin:

Reply 383

Mattywooda

Original post by TheStudent.

I guess that makes sense, but the F-S-F thing threw me off. I'm probably wrong :tongue:

http://en.wikipedia.org/wiki/Sulfur_hexafluoride

The most trustworthy of sources =P But look at the diagram definitely 90.

Reply 384

TheStudent.

Original post by AGrumpyMole

12.5 moles of OXYGEN react with 1 mole of octane
so 60cm3 * 12.5 = 0.75 dm^3
0.75 = 21% of air
(0.75/21)*100 = 3.57dm^3

Oooh I did that a completely different way but got 3.57.

I did 12.5 x 24 = Blank
21% of that..
And can't remember what I did afterwards.

I got there eventually LOL.

Reply 385

AGrumpyMole

Original post by Mattywooda

http://en.wikipedia.org/wiki/Sulfur_hexafluoride

The most trustworthy of sources =P But look at the diagram definitely 90.

It depends if, by F-S-F, it ment the bond angles in SF6, or a separate SF2 molecule

Reply 386

TheStudent.

Original post by Mattywooda

http://en.wikipedia.org/wiki/Sulfur_hexafluoride

The most trustworthy of sources =P But look at the diagram definitely 90.

Original post by ChloeTredinnick

This question was stupid.
So would i get the marks for using them as two seprerate molecules

Haha

I know that octrahedral = 90 degrees, but the only reason why I changed my answer was because they said, state the bond angle of F-S-F. Which in my mind, was 109 degrees.

Ermmmmm, it depends on whether the examiner realises that you said its both octrahedral and tetrahedral. If he does, then you'd probably lose the mark. Buutttttt, you'll only have lost 1 mark out of 4, so don't stress :smile:

Reply 387

dongonaeatu

Original post by TheStudent.

I said 109 degrees.. I explained why on pageee 17 I think.
Advantage - water is the only product
Disadvantage - must be stored in a high pressure fuel tank

Ionic lattice + conducts electricity only when molten or in solution ( you could also say its usually soluble )

ur wrong its 90 cgp

Reply 388

TheStudent.

Original post by AGrumpyMole

It depends if, by F-S-F, it ment the bond angles in SF6, or a separate SF2 molecule

Yehh it was so unclear!

Reply 389

TheStudent.

Original post by dongonaeatu

ur wrong its 90 cgp

Reply 390

matty b

PLEASE. CAN WE DECIDE WHAT THE ANGLE WAS?

Was it 109 or 90.

Reply 391

dongonaeatu

Original post by TheStudent.

in cgp it says all bonds in sf6 are 90 degrees

Reply 392

Chris..

Original post by matty b

PLEASE. CAN WE DECIDE WHAT THE ANGLE WAS?

Was it 109 or 90.

Reply 393

TheStudent.

Original post by matty b

PLEASE. CAN WE DECIDE WHAT THE ANGLE WAS?

Was it 109 or 90.

Original post by AGrumpyMole

It depends if, by F-S-F, it ment the bond angles in SF6, or a separate SF2 molecule

LOL

This.

Reply 394

twizzzzzzter

The F-S-F question will no doubt be mentioned in the examiners report

Reply 395

TheStudent.

Original post by dongonaeatu

in cgp it says all bonds in sf6 are 90 degrees

Yehh thats right :tongue:

but thats not why I said it was 109.

Reply 396

Reina

What did people put for definition of "clean burn fuels"?

Reply 397

TheStudent.

Original post by Reina

What did people put for definition of "clean burn fuels"?

Complete combustion, when reacted with O2 to produce CO2 and H20. No CO produced.

Reply 398

Chris..

in the question it said what the bond angle on the F-S-F... as opposed to whats the bond angle on a F-S-F..

Reply 399

AGrumpyMole

Original post by TheStudent.

LOL

This.

I thought, if it had ment the bond angles in SF6, it would be 90 (S-F bond angle)
and, if it ment the bond angles in F-S-F, it would be 109 (or 104.5 to be more precise) due to the 2 lone pairs and 2 bonding pairs. I put 109....