HSC Chemistry Question Thread

[MisterNeo]

For states in chemical reactions, are they for the chemical at standard conditions or state in the reaction?

For eg.
Hydration of ethene, is the water and ethanol gas or liquid?

Thank you

It depends on the conditions in which the reaction takes place.
For the hydration of ethene, it is done at 300^oC. This means that the water and ethanol will be gases in the equation.
For combustion, it is usually done at room temperature. This means that the water product will be written as a liquid. (Combustion heat is a product, not a condition.)

[anotherworld2b]

How do you do this question 7?

[J.B]

It depends on the conditions in which the reaction takes place.
For the hydration of ethene, it is done at 300^oC. This means that the water and ethanol will be gases in the equation.
For combustion, it is usually done at room temperature. This means that the water product will be written as a liquid. (Combustion heat is a product, not a condition.)

Ok, Thank you.

Also I was just wondering for the Industrial production of LDPE is the process called Free Radical polymerisation, and for the production of HDPE is the process called Zieglar-Natta Process?

Thank you

[Shadowxo]

How do you do this question 7?

You know the initial mass was 8.2g including the water, and when the water was removed (resulting in anhydrous zinc sulphate) you ended up with 4.6g. So, the mass of water in the original sample was (8.2-4.6) = 3.6g
Mass ZnSO₄ : Mass H₂O
4.6  :  3.6
mol ZnSO₄ : mol H₂O
4.6/161 : 3.6/18
0.0286 : 0.2
1 : 0.2/0.0286
1 : 7
So x=7, as there's 7 H₂O molecules for every ZnSO₄ molecule

[bsdfjnlkasn]

Ok, Thank you.

Also I was just wondering for the Industrial production of LDPE is the process called Free Radical polymerisation, and for the production of HDPE is the process called Zieglar-Natta Process?

Thank you

Hey there!

This is what I have

LDPE: Free radical process
HDPE: Ziegler Natta Process (or Catalysis)

[anotherworld2b]

You know the initial mass was 8.2g including the water, and when the water was removed (resulting in anhydrous zinc sulphate) you ended up with 4.6g. So, the mass of water in the original sample was (8.2-4.6) = 3.6g
Mass ZnSO₄ : Mass H₂O
4.6  :  3.6
mol ZnSO₄ : mol H₂O
4.6/161 : 3.6/18
0.0286 : 0.2
1 : 0.2/0.0286
1 : 7
So x=7, as there's 7 H₂O molecules for every ZnSO₄ molecule

Thank you for your help
I was also working on this question but I got stuck on part a. This is what I have so far

Mod edit: Merged posts

[MisterNeo]

I was also working on this question but I got stuck on part a. This is what I have so far

Make sure you write the formulas correctly.
For this question, you'd find moles of the ammonium h-phosphate produced and work backwards to find the calcium phosphate contained in the original 60kg.

[J.B]

I was just wondering if membrane filters be used to reduce eutrophication?
Thanks

[MisterNeo]

I was just wondering if membrane filters be used to reduce eutrophication?
Thanks

Reverse osmosis probably can prevent eutrophication because it can remove small molecules from water, such as nitrates and phosphates.

[J.B]

Reverse osmosis probably can prevent eutrophication because it can remove small molecules from water, such as nitrates and phosphates.

Thank you

I also have a couple more questions:
 I was also wondering what is the difference between Dissolved ions and TDS? As they are two separate things in the syllabus?

And in the industrial chemistry option my class did not do the Sulfuric acid oxidising practical. So I was just wondering what observations are made between the reaction of hot concentrated sulfuric acid and copper? And what exact concentration of Sulfuric acid is needed?

Also are these the correct states in the equation?

Copper Oxidises:                Cu(s) ->  Cu2+(aq) + 2e-
Sulfuric acid reduces:        2H2SO4 (aq) + 2e-   ->   SO2 (g) + 2H2O(l) + SO42-(aq)

Overall Reaction:    Cu(s) + 2H2SO4 (aq) ->  CuSO4 (aq) + SO2 (g) + 2H2O(l)

I have also read that Conc. Sulfuric Acid can oxidised only those below lead of standard potentials producing SO2, but then was told that Conc. Sulfuric Acid can oxidise those above lead as well producing SO2. I'm just wondering which one is correct?


And in a soap molecule, in water does the Na+ and Negative fatty acid chain separate (dissolve)?
Thanks

[arunasva]

Anyone doin SHIPWRECKS ?

Is corrosion faster in Neutral or Alkaline environment considering everything else is constant in the environment ? Ik acidic is the fastest.

[MisterNeo]

Thank you

I also have a couple more questions:
 I was also wondering what is the difference between Dissolved ions and TDS? As they are two separate things in the syllabus?

And in the industrial chemistry option my class did not do the Sulfuric acid oxidising practical. So I was just wondering what observations are made between the reaction of hot concentrated sulfuric acid and copper? And what exact concentration of Sulfuric acid is needed?

Also are these the correct states in the equation?
Copper Oxidises:                Cu(s) ->  Cu2+(aq) + 2e-
Sulfuric acid reduces:        2H2SO4 (aq) + 2e-   ->   SO2 (g) + 2H2O(l) + SO42-(aq)
Overall Reaction:    Cu(s) + 2H2SO4 (aq) ->  CuSO4 (aq) + SO2 (g) + 2H2O(l)

I have also read that Conc. Sulfuric Acid can oxidised only those below lead of standard potentials producing SO2, but then was told that Conc. Sulfuric Acid can oxidise those above lead as well producing SO2. I'm just wondering which one is correct?

And in a soap molecule, in water does the Na+ and Negative fatty acid chain separate (dissolve)?
Thanks

Dissolved ions is exactly what the name suggests...cations and anions in water. Total dissolved solids, however, include everything dissolved in water that used to be a solid, such as soluble salts, fine dirt particles, sugar, cow shit, etc.
Observations from the prac would include the release of sulfur dioxide gas (bubbles), which you must prove was actually sulfur dioxide using moist litmus paper. The brown copper will become a bluish-white copper sulfate. (Anhydrous is white, pentahydrate is blue. The acid will dehydrate some of it.) The sulfuric acid is very concentrated at around ~98%.
Your equations must have sulfuric acid as a liquid when used on copper or to dehydrate something. Other than that, the rest looks fine. I'm not sure about the reduction table question since you wouldn't need to go into that much detail. But, I would say above lead towards potassium (I may be wrong).
Soaps do dissociate in solution to release the sodium/potassium ion.

[J.B]

Dissolved ions is exactly what the name suggests...cations and anions in water. Total dissolved solids, however, include everything dissolved in water that used to be a solid, such as soluble salts, fine dirt particles, sugar, cow shit, etc.
Observations from the prac would include the release of sulfur dioxide gas (bubbles), which you must prove was actually sulfur dioxide using moist litmus paper. The brown copper will become a bluish-white copper sulfate. (Anhydrous is white, pentahydrate is blue. The acid will dehydrate some of it.) The sulfuric acid is very concentrated at around ~98%.
Your equations must have sulfuric acid as a liquid when used on copper or to dehydrate something. Other than that, the rest looks fine. I'm not sure about the reduction table question since you wouldn't need to go into that much detail. But, I would say above lead towards potassium (I may be wrong).
Soaps do dissociate in solution to release the sodium/potassium ion.

Thank you

And would the copper metal dissolve or does the copper sulfate become a solid?

[MisterNeo]

Thank you

And would the copper metal dissolve or does the copper sulfate become a solid?

The resulting copper sulfate would be aqueous because water is also produced and the conc. acid has 2% water in it. So the equation would have aqueous copper sulfate.

[Aaron12038488]

I need help with the steps involved LDPE such as Initiation, Propagation, termination. I'm confused with diagrams to support the description of each step.