Question 4???

[Tashi]

Haha oh dear, I couldn't even think at that point so I said it would stay the same because the water content doesn't affect the percentage of P205. Hopefully that's at least one mark.

[stonecold]

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?

This.  'Deliberately' meant to use the new formula.  No change is the only correct answer IMO.

If you explained that you used the old formula then maybe you will get marks.

[lilaznkev1n]

would i get any marks for the first part if i worked out the mole of precipitate correctly and used the corrected method for working out percentage (mass i got / mass fertiliser *100) and the rest i got wrong like the mole ratio etc... ?

[jamo727]

it was a 3 or 4 mark question, so you should get a mark or two for getting those correct id imagen

[funkyducky]

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

It was very ambiguous. I said same, provided that the molar mass of the product was used in calculations, because none of the phosphorous had been evaporated out. Sound good enough for the marks?

[luken93]

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

It was very ambiguous. I said same, provided that the molar mass of the product was used in calculations, because none of the phosphorous had been evaporated out. Sound good enough for the marks?

I did the same as you, so imma gonna say yes hahahaha

[Milkshake]

it was a 3 or 4 mark question, so you should get a mark or two for getting those correct id imagen

How many marks would I get for using a mole ratio of 1:1, and getting a percentage of like 70 something for 4a?

[Greatness]

it was a 3 or 4 mark question, so you should get a mark or two for getting those correct id imagen

How many marks would I get for using a mole ratio of 1:1, and getting a percentage of like 70 something for 4a?

+1 Id say one mark at least hahah

[scocliffe09]

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?

This.  'Deliberately' meant to use the new formula.  No change is the only correct answer IMO.

If you explained that you used the old formula then maybe you will get marks.

I'm with stonecold (again). Deliberatly = the same.

[phallyy]

I find stoich challenging! I took a guess! Does anyone know where I can actually have a look at the question again, or perhaps someone can post it up here ?

[scocliffe09]

I find stoich challenging! I took a guess! Does anyone know where I can actually have a look at the question again, or perhaps someone can post it up here ?

The paper is here: http://vce.atarnotes.com/forum/index.php/topic,42632.0.html
the suggested solutions are here: www.connecteducation.com.au