VCE Chemistry Question Thread

[Adequace]

Hey guys, could I have some help with part d http://m.imgur.com/a/BOkM8 ?

My working was a bit of a guess since I'm pretty lost for this part.

[mary1911997]

help PLEASE

I have done a prac and a question states
the actual values for the heat of formation of magnesium nitrate, zinc nitrate, lead nitrate are given below
magnesium nitrate = -790 kJ/mol
zinc nitrate = -564 KJ/mol
lead nitrate = -447 KJ/mol

how do your values compare and give two reasons which could account for any difference
knowing that my results were
magnesium nitrate = -434kJ/mol
zinc nitrate = -67KJ/mol
lead nitrate = -211KJ/mol

[sweetcheeks]

Hey guys, could I have some help with part d http://m.imgur.com/a/BOkM8 ?

My working was a bit of a guess since I'm pretty lost for this part.

You are taking a 1/5 sample of the solution and adding it to 700ml. Work out how many grams of sodium nitrate you have in the 250ml and divide by 5 to find the amount of sodium nitrate that is in the sample. In the new solution there will be a total volume of 750ml (50ml sample + 700ml water).

Divide the amount of sodium nitrate in the solution by the volume (0.750 litres) of solution to find the amount in grams per litre.

[sweetcheeks]

help PLEASE

I have done a prac and a question states
the actual values for the heat of formation of magnesium nitrate, zinc nitrate, lead nitrate are given below
magnesium nitrate = -790 kJ/mol
zinc nitrate = -564 KJ/mol
lead nitrate = -447 KJ/mol

how do your values compare and give two reasons which could account for any difference
knowing that my results were
magnesium nitrate = -434kJ/mol
zinc nitrate = -67KJ/mol
lead nitrate = -211KJ/mol

Lets take a look at these results. All reactions tested are exothermic, releasing heat. All the values you received in your results are lower than that of expected values. Why may there have been less energy detected than expected?

Loss of heat to the environment?

Impurities in the samples? water in the samples?

Calorimeter incorrectly calibrated?

Inaccurate reading of thermometer?

[mary1911997]

Lets take a look at these results. All reactions tested are exothermic, releasing heat. All the values you received in your results are lower than that of expected values. Why may there have been less energy detected than expected?

Loss of heat to the environment?

Impurities in the samples? water in the samples?

Calorimeter incorrectly calibrated?

Inaccurate reading of thermometer?

Thanks got it now   

[knightrider]

Are the questions in the neap smartstudy questions for units 3 and 4 chemistry exam standard?

Are they good preparation for VCAA exams ?

Thanks 

[sweetiepi]

Are the questions in the neap smartstudy questions for units 3 and 4 chemistry exam standard?

Are they good preparation for VCAA exams ?

Thanks 

From my experience, NEAP go through core understanding, rather than VCAA style, per say, however, there is a bit of crossover too.
I'd recommend NEAP to consolidate knowledge first.


(Mods: correct me if wrong )

[knightrider]

From my experience, NEAP go through core understanding, rather than VCAA style, per say, however, there is a bit of crossover too.
I'd recommend NEAP to consolidate knowledge first.


(Mods: correct me if wrong )

Thankyou insanipi 

so do you think practice exams other than VCAA are better for preparing you for the real exam( would it be better to go straight into prac exams or do the neap smartstudy stuff 1st?

[Sine]

From my experience, NEAP go through core understanding, rather than VCAA style, per say, however, there is a bit of crossover too.
I'd recommend NEAP to consolidate knowledge first.


(Mods: correct me if wrong )

Neap is way more in depth in than VCAA stuff, having said that have a look at a couple of VCAA exams so that you know the style of questions and be able to better gauge which companies have the "better" (more similar to VCAA) trial exams.

Currently i'm only starting to do Unit 3 trial exams.

Thankyou insanipi 

so do you think practice exams other than VCAA are better for preparing you for the real exam( would it be better to go straight into prac exams or do the neap smartstudy stuff 1st?

Depends how well you know your stuff I think. Maybe have a go one trial exam and see how you go.
... but definitely do prac exams last so by that logic neap smartstudy 1st. (that's if you want to do both)

[sweetiepi]

Thankyou insanipi 

so do you think practice exams other than VCAA are better for preparing you for the real exam( would it be better to go straight into prac exams or do the neap smartstudy stuff 1st?

You're most welcome!

Consolidating knowledge first using NEAP usually is my priority, however throughout this year, I've had VCAA questions for homework (because teacher knows what she's doing).
In short, I'd recommend definitely doing a few NEAP then switch it up between VCAA and some others. It gives you an understanding of questions you may need to do in different circumstances (Such as SACs), not just the final exam.

But I'd recommend VCAA papers as the best indicator of what is going to be on the exams, and you should leave the past few years to attempt last.

I hoped I answered your question.

(Also Sine's advice is 100% ace )

[knightrider]

Neap is way more in depth in than VCAA stuff, having said that have a look at a couple of VCAA exams so that you know the style of questions and be able to better gauge which companies have the "better" (more similar to VCAA) trial exams.

Currently i'm only starting to do Unit 3 trial exams.Depends how well you know your stuff I think. Maybe have a go one trial exam and see how you go.
... but definitely do prac exams last so by that logic neap smartstudy 1st. (that's if you want to do both)

You're most welcome!

Consolidating knowledge first using NEAP usually is my priority, however throughout this year, I've had VCAA questions for homework (because teacher knows what she's doing).
In short, I'd recommend definitely doing a few NEAP then switch it up between VCAA and some others. It gives you an understanding of questions you may need to do in different circumstances (Such as SACs), not just the final exam.

But I'd recommend VCAA papers as the best indicator of what is going to be on the exams, and you should leave the past few years to attempt last.

I hoped I answered your question.

(Also Sine's advice is 100% ace )

Thankyou so so much Sine and insanipi . Really appreciate it !!! 

[larissaaa_]

What does the dot in a chemical equation represent? I know it's like a multiplication sign, but what does that mean?

[sweetiepi]

What does the dot in a chemical equation represent? I know it's like a multiplication sign, but what does that mean?

As in CuSO₄.H₂O? It means something is hydrated or that water/another compound is attached to the main compound.

Hope this helps.

[larissaaa_]

As in CuSO₄.H₂O? It means something is hydrated or that water/another compound is attached to the main compound.

Hope this helps.

Thank you! So in the case you mentioned, it would mean that the copper sulfate was hydrated?

[sweetiepi]

Thank you! So in the case you mentioned, it would mean that the copper sulfate was hydrated?

Most welcome!
Yep. The copper sulphate would be hydrated in this case, however sometimes you can see copper sulphate and water separately- such as CuSO₄ + H₂O - which obviously isn't hydrated, as well.