Ocr f321 23 may 2013~official discussion thread

Original post by trrr

PH3- vdw forces

NH3- Hydrogen bonds

Ok i need help
in the box in the question for the bonding of PH3 AND NH3
which one was at the top- because i just remember writing h-bond for the top one and VDW for the bottom one??
:titan:

(edited 10 years ago)

Reply 763

Ferrari_1996

10

Original post by Meee.

For the avagadro constant question did you have to divide the number of atoms by 5 because they were asking for the number of molecules? (And there were 5 atoms per molecule)

I didn't divide by 5. But maybe you had to. Did you divide by 5?

Reply 764

Original post by yodawg321

Second question on the paper. Asking about Protons neutrons and electrons

Well is it was an isotope the electrons and protons stay the same and only the neutrons change, so yeah it was that, I forgot about that answer

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Reply 765

yodawg321

12

Original post by Ferrari_1996

I didn't divide by 5. But maybe you had to. Did you divide by 5?

I didn't divide by 5 :/

Reply 766

Original post by Meee.

For the avagadro constant question did you have to divide the number of atoms by 5 because they were asking for the number of molecules? (And there were 5 atoms per molecule)

Why divide by 5? It wasn't needed if I've remembered correctly.

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Reply 767

anonymousecheese

i didnt notice that :unimpressed:

Reply 768

Meee.

1

Original post by Ferrari_1996

I didn't divide by 5. But maybe you had to. Did you divide by 5?

Yeh because the avagadro constant gives you the number of atoms, not number of molecules. Plus it was 3 marks! Otherwise it would've been a 2 marker?

Reply 769

Kitnimohabbathai

what the 5 marker just about reactivity increasing down group 2?

Reply 770

abudabu

Did anyone get 3.01 x 10^22 for the avongardo constant q?

Reply 771

k1rby

10

Original post by Meee.

For the avagadro constant question did you have to divide the number of atoms by 5 because they were asking for the number of molecules? (And there were 5 atoms per molecule)

I did that but I've checked online and we were meant to do the 0.05 moles times by avogadro's constant. We'll probably get 2 out of 3 marks though.

http://www.ehow.com/how_8463162_number-molecules-compound-given-grams.html

Reply 772

Kitnimohabbathai

Original post by abudabu

Did anyone get 3.01 x 10^22 for the avongardo constant q?

yep

Reply 773

Original post by Meee.

Yeh because the avagadro constant gives you the number of atoms, not number of molecules. Plus it was 3 marks! Otherwise it would've been a 2 marker?

Oh. I forgot that, I'm feeling like I've only got about 52-54 now :-/

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Reply 774

trrr

13

Original post by abudabu

Did anyone get 3.01 x 10^22 for the avongardo constant q?

What question was that?

Reply 775

Original post by abudabu

Did anyone get 3.01 x 10^22 for the avongardo constant q?

Same here!

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Reply 776

MrJiggly

Original post by Meee.

For the avagadro constant question did you have to divide the number of atoms by 5 because they were asking for the number of molecules? (And there were 5 atoms per molecule)

I thought that didn't matter. I thought 1 mol was 6.02X10^23 for any particles. So like 1 mole of a grain of sand= 6.02X10^23 sand compound. So wouldn't 1 mol of a molecule just be 6.02X10^23 molecules?

Reply 777

Liberty.

10

Original post by k1rby

I did that but I've checked online and we were meant to do the 0.05 moles times by avogadro's constant. We'll probably get 2 out of 3 marks though.

http://www.ehow.com/how_8463162_number-molecules-compound-given-grams.html

I divided by 5 too :frown:

It makes more sense, sneaky question!

Reply 778

Kitnimohabbathai

Original post by anonymousecheese

Ok i need help
in the box in the question for the bonding of PH3 AND NH3
which one was at the top- because i just remember writing h-bond for the top one and VDW for the bottom one??
:titan:

yeah that's fine...nh3 was at the top :smile:

Reply 779

MrJiggly