Ocr f321 23 may 2013~official discussion thread

No problem, you may have gotten a mark for VDW forces, as everything technically has slight VDW forces between them, but I'd doubt you'd get full marks. Was it a 1 or 2 mark question?

I think one mark was for n = m/RMM, one mark was for multiplying by avagadro's, and also one mark was to show whether or not you realized what a mole actually was an you didn't need to multiply by 4.

Yes, as you can almost treat the molecules as atoms if you like. If you had 1 mole of Helium atoms, it would be the same number of molecules as 1 mole of O₂ molecules and yet twice the number of atoms. It asked for the number of molecules not atoms.

There was 2 bits to it so the table and then the explanation for why NH3 's mp was higher so in total it was 2 marks I'm hoping I got ECF though

That's what I got

Seemed too little for 3 marks!

No problem, you may have gotten a mark for VDW forces, as everything technically has slight VDW forces between them, but I'd doubt you'd get full marks. Was it a 1 or 2 mark question?

Would I get the mark for stupidly putting concentrated ammonia 'solution' rather than just concentrated ammonia


Posted from TSR Mobile

Would I get the mark for stupidly putting concentrated ammonia 'solution' rather than just concentrated ammonia


Posted from TSR Mobile

Does multiplying the number of moles by avagadro's constant give you the number of atoms? I don't understand why that's the same as the number of molecules.

I'm not complaining, of course, because if you're right, I got the question right. I'm just curious, that's all.

u thought the gas was 360 ... what's this about 1080?

i found 0.05 as the mol and then i x5 because there was 5 molecules in SiCl4 then i got 0.25 which i then x it by the avogadro number and i got 1.505x10^23 correct me if im wrong i want to see why its not that

no. A mole is a constant (6.02x10²³), and so if you have say 1 mole of something (ANYTHING), you will have 6.02x10²³ of it. That can be atoms, molecules, grains of sand, planets, anything. So if you have 0.05 moles of SiCl₄, then to find the number of molecules, you have to times AGadro's constant by the number of moles.

Reason why I don't think a mark will be awarded for VDW is because the heading of the table specifically stated 'main type of bonding' acknowledging the fact that both PD-PD and VDW will be present. I myself put VDW =\, yet again didn't read through the question propperly.

no. A mole is a constant (6.02x10²³), and so if you have say 1 mole of something (ANYTHING), you will have 6.02x10²³ of it. That can be atoms, molecules, grains of sand, planets, anything. So if you have 0.05 moles of SiCl₄, then to find the number of molecules, you have to times AGadro's constant by the number of moles.

Does multiplying the number of moles by avagadro's constant give you the number of atoms? I don't understand why that's the same as the number of molecules.

I'm not complaining, of course, because if you're right, I got the question right. I'm just curious, that's all.