Question 4???

[superstar1]

i found this question really confusing and wanted to noe if anyone got higher in part b?

[alexvuuuuu]

It's supposed to be the same, since the moles of P2O5 doesn't change. Also, you were given to formula for the precipitate, so it doesn't affect the mass of P2O5. I'm pretty sure

[nemolala]

did you get 73.7%?

[AleksIlia]

did you get 73.7%?

I got around 38 or 36% can't remember exactly, pretty sure you had to divide n(P) by 2 for n(P2O5) as the precipitate only had one P. I think if you divided your percentage by 2 you would have got the answer

[dmanz]

i got 33%

[superstar1]

yeh im sure the first part was 36.8% but i still cant grasp the idea of the second part?

[BoredSatan]

i found this question really confusing and wanted to noe if anyone got higher in part b?

I also got higher but i know its wrong..

cause when you heat it, the mass & molar mass changes..

[Milkshake]

When you heat it, you will drop mass because you lost water. The molar mass of the compound will also decrease because of the lost water. However the mass of phosphate stays the same, because the question said to assume that all the phosphate is converted. So m(P) stays the same, therefore the % is the same aswell

[superstar1]

but wasny the mass constant assuming that it was dried before hand anyway???

oh now i got it.. thanks

[pi]

Yeh, it was like 36.8%.

When you heat it, you will drop mass because you lost water. The molar mass of the compound will also decrease because of the lost water. However the mass of phosphate stays the same, because the question said to assume that all the phosphate is converted. So m(P) stays the same, therefore the % is the same aswell

But the assumption made is that calculations are made using the old molar mass?

[GuessWho]

Yeh, it was like 36.8%.

When you heat it, you will drop mass because you lost water. The molar mass of the compound will also decrease because of the lost water. However the mass of phosphate stays the same, because the question said to assume that all the phosphate is converted. So m(P) stays the same, therefore the % is the same aswell

But the assumption made is that calculations are made using the old molar mass?

It said that it was deliberately heated to above 100 degrees which leads me to think that he would've realised that the Molecular formula would have changed and would then have done calculations accordingly?

[pi]

Not entirely convinced... Seems a bit ambiguous and overly-complex compared to similar questions of previous years. We'll see in the assessor's report

[Water]

No entirely convinced... We'll see in the assessor's report

Estimate when the assessor's report is released? Or is it one of those ambigious things?

[pi]

No entirely convinced... We'll see in the assessor's report

Estimate when the assessor's report is released? Or is it one of those ambigious things?

Dunno, usually a few months though. Though, I'm not to keen on it really. It's not as if I can change anything.

[nemolala]

what wrong with VCAAAAAAAAAAA