HSC Chemistry Question Thread

[bridie_2345]

Hey there I was wondering if this is how you represent rhthe ionisation of phosphoric acid? The answer in the back of the text book isn't clear. Thanks heaps! 😊

[MisterNeo]

Hey there I was wondering if this is how you represent rhthe ionisation of phosphoric acid? The answer in the back of the text book isn't clear. Thanks heaps! 😊

Phosphoric acid is a weak acid, so the first two arrows should be an equilibrium like the third.



Make sure you write states on all the species and some of the hydronium are missing plus charges. Also on the second and third line, it reacts with water, not hydronium.
But it looks like you have a good understanding of acid protonation.

[mylinh-nguyen]

I don't get how to do this

[MisterNeo]

I don't get how to do this

(v/v%) is equal to volume of ozone divided by volume of solution, then multiplied by 100. To calculate ppm, divide 0.000002% by 100 to get 0.00000002L per 1L of air. Multiply this by 1000000 to get the litres of ozone for every million litres of air, which is 0.02ppm.

[mylinh-nguyen]

(v/v%) is equal to volume of ozone divided by volume of solution, then multiplied by 100. To calculate ppm, divide 0.000002% by 100 to get 0.00000002L per 1L of air. Multiply this by 1000000 to get the litres of ozone for every million litres of air, which is 0.02ppm.

thank you!

[justwannawish]

How should we structure an extended response about the use of ethanol to society?
Are the main advantages it is renewable, biodegradable and can be made out of waste products of cellulose?
The disadvantages: expensive to manufacture, fuel inefficient, uses a lot of energy and land to produce in large quantities?

[winstondarmawan]

How should we structure an extended response about the use of ethanol to society?
Are the main advantages it is renewable, biodegradable and can be made out of waste products of cellulose?
The disadvantages: expensive to manufacture, fuel inefficient, uses a lot of energy and land to produce in large quantities?

Start with your criteria, which is a restatement of the question in your own words.
Then you would start with advantages:
1.
2.
3.
etc. Then the disadvantages.
After that, a judgement is required. So basically here you will sum up your points and say that 'Due to the advantages and disadvantages discussed above, ethanol has high potential in benefiting society as a fuel source, however at the current stage the disadvantages outweigh the advantages in terms of completely replacing crude oil. However, it is still effective as a fuel extender thus minimising the strain on natural reserves of crude oil and with greater production efficiency in the future will definitely see a rise in usage.

Hope this helps.

[winstondarmawan]

Shipwrecks:
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22290341_1343710039087849_1169313217_n.jpg?oh=38c0aa9bb7f45af267b33b47963eceea&oe=59D96F7D
Can't find enough to write for 7 marks... would appreciate help with this.
Thanks in advance!

[justwannawish]

Start with your criteria, which is a restatement of the question in your own words.
Then you would start with advantages:
1.
2.
3.
etc. Then the disadvantages.
After that, a judgement is required. So basically here you will sum up your points and say that 'Due to the advantages and disadvantages discussed above, ethanol has high potential in benefiting society as a fuel source, however at the current stage the disadvantages outweigh the advantages in terms of completely replacing crude oil. However, it is still effective as a fuel extender thus minimising the strain on natural reserves of crude oil and with greater production efficiency in the future will definitely see a rise in usage.

Hope this helps.

Thanks
How many advantages/disadvantages do we need for a response for 5 marks vs something that's 7?

[Natasha.97]

Thanks
How many advantages/disadvantages do we need for a response for 5 marks vs something that's 7?

Hi!

Not 100% sure on this but I would allocate 1 mark for the judgement, so that leaves 4 marks for the first scenario (2 advantages, 2 disadvantages) and 6 marks for the second scenario (3 advantages, 3 disadvantages)

[justwannawish]

Hi!

Not 100% sure on this but I would allocate 1 mark for the judgement, so that leaves 4 marks for the first scenario (2 advantages, 2 disadvantages) and 6 marks for the second scenario (3 advantages, 3 disadvantages)

Ooh, thank you for such a quick reply! I always end up giving the same amount of reasons for 5-8 mark questions because I don't want to lose marks on not writing down things I did know because I underestimated the question's worth!

[Henry Kocatekin]

For 1 Mark chemical equations, do you need the states?

And the same for 2 markers of the same type.

[justwannawish]

For 1 Mark chemical equations, do you need the states?

And the same for 2 markers of the same type.

Not sure but include it just in case. You don't want to be marked down by such a simple thing

[MisterNeo]

For 1 Mark chemical equations, do you need the states?

And the same for 2 markers of the same type.

Always have states in all your equations. I lost quite a few marks for this in Prelims. The only species that don’t need states are electrons (in galvanic questions) and free radicals (in ozone and polymerisation).

[bdobrin]

Hi jake,

I just went to your chemistry HSC lecture last week - i thought it was great.

Im just a little confused on what is a polymer, monomer and a radical.

Thanks,
Ben