HSC Chemistry Question Thread

[RuiAce]

Hi all,
I was hoping someone could help me with this question. I understand that A is endothermic and thus has +ΔH, and I also figure that C must have +ΔH as it is the reverse of a combustion reaction. However, I am unsure of B and D and how to identify their ΔH value as positive or negative.
Thanks

This is completely stretching the boundaries the HSC course, but I see your Victorian tag so you might've posted in the wrong section of the forum.

Intuitive explanation: The reactions that happen spontaneously are the exothermic ones; you need to provide energy for an endothermic one. Sodium metal, being as reactive as it is, would more likely spontaneously lose off that electron to become a sodium ion. Reaction B (the reverse) is unlikely to be spontaneous and is thus also the endothermic one.

[kylesara]

Hi, if basic oxides contain metals, and acidic oxides contain non-metals, why is NH3 basic? Thanks

[RuiAce]

Hi, if basic oxides contain metals, and acidic oxides contain non-metals, why is NH3 basic? Thanks

NH3 is not an oxide.

You don't have to be an oxide to be basic/acidic. They're defined by the Bronsted-Lowry definition of proton acceptors/donors, not the presence of an oxygen.

[legorgo18]

Hi guys, just a few questions on nuclear chemistry from pom 9.2.5

1)Do you need to know about nuclear fusion
2)Are there any cons for tc 99m and na24 (i cant find any)
3) What is synchrotron and do you need to know it

ty

[jakesilove]

Hi guys, just a few questions on nuclear chemistry from pom 9.2.5

1)Do you need to know about nuclear fusion
2)Are there any cons for tc 99m and na24 (i cant find any)
3) What is synchrotron and do you need to know it

ty

Hey!

1) For the Nuclear chem dotpoints, no you don't. However, if you're doing Industrial chemistry as an option, you learn about it there!

2) Just use standard disadvantages. Eg. radioactive waste, cost to produce, ability to potentially harm humans, over exposure etc.

3) A synchrotron is just a particle accelerator! That's definitely something you need to know about; it's basically a massive circle that accelerates charged particles to near light speed, then smashes it into another particle.

Let me know if you have any more questions!

[legorgo18]

Hi jake! Thanks for the response, for the synchrotron if i use copernicium as an example, what would be the nuclear eqn?

And i just need some clarification on the transuranic and commercial production dot points,
so basically they have the same methods but commercial can only be produced by cyclotron and nuclear reactor? Sorry i just want to make sure i get this correct in my test if it pops up

[jakesilove]

Hi jake! Thanks for the response, for the synchrotron if i use copernicium as an example, what would be the nuclear eqn?

And i just need some clarification on the transuranic and commercial production dot points,
so basically they have the same methods but commercial can only produced by cyclotron and nuclear reactor? Sorry i just want to make sure i get this correct in my test if it pops up

Don't choose an element and then see if it works for something like a particle accelerator; spend some time googling particle accelerators, and find a reaction that occurs.

I don't quite understand your question; cyclotrons and nuclear reactors are two completely different things, and have different methods of producing transuranic elements. You need to understand how both of them work, and the differences between the two. They are both used for commercially produced isotopes.

[RuiAce]

Hey!

1) For the Nuclear chem dotpoints, no you don't. However, if you're doing Industrial chemistry as an option, you learn about it there!

I don't think so

Hi jake! Thanks for the response, for the synchrotron if i use copernicium as an example, what would be the nuclear eqn?

And i just need some clarification on the transuranic and commercial production dot points,
so basically they have the same methods but commercial can only be produced by cyclotron and nuclear reactor? Sorry i just want to make sure i get this correct in my test if it pops up

Your nuclear equation does not have to be related to the synchrotron. There's no point in memorising an equation just for a specific type of particle accelerator.

You only need an equation to demonstrate production of a transuranic element (which Copernicium suffices for), and one for transuranic element. Not for each type of particle accelerator.

Nuclear equations are a thing to which Wikipedia can be deemed reliable.

[legorgo18]

I was just asking about the difference between the 2, or if this statement is correct:

transuranic can be produced by nuclear reactor, linear accelerator and cyclotron and commercial can only be produced by nuclear reactor and cyclotron

[kiwiberry]

Hey, I'm a bit confused about which equations to use for the formation of acid rain. My teacher gave me these:
SO_2(g) + H₂O_(l) --> H₂SO_3(aq) (also is this supposed to be in equilibrium?)
SO_3(g) + H₂O_(l) --> H₂SO_4(aq)

but my textbook has this one instead of the second one:
2H₂SO_3(aq) +O_2(g) --> 2H₂SO_4(aq)

Or are they both correct?

[RuiAce]

Hey, I'm a bit confused about which equations to use for the formation of acid rain. My teacher gave me these:
SO_2(g) + H₂O_(l) --> H₂SO_3(aq) (also is this supposed to be in equilibrium?)
SO_3(g) + H₂O_(l) --> H₂SO_4(aq)

but my textbook has this one instead of the second one:
2H₂SO_3(aq) +O_2(g) --> 2H₂SO_4(aq)

Or are they both correct?

There's actually TWO reaction pathways to make sulfuric acid.

The O₂ can bump into the SO₂ first, or the H₂O does.

[kiwiberry]

There's actually TWO reaction pathways to make sulfuric acid.

The O₂ can bump into the SO₂ first, or the H₂O does.

Ah I see, thank you

[Butterflygirl]

Guys, I'm so confused about the states of hydrocarbons...

For combustion, we did a prac with a burner that contained ethanol in liquid form but the teacher said that in the equation for combustion of ethanol, it should be in gas state.

Can someone tell me how to figure out the state of different hydrocarbons?


Thankyou!!

[RuiAce]

Guys, I'm so confused about the states of hydrocarbons...

For combustion, we did a prac with a burner that contained ethanol in liquid form but the teacher said that in the equation for combustion of ethanol, it should be in gas state.

Can someone tell me how to figure out the state of different hydrocarbons?


Thankyou!!

I think the reason why it's gaseous is simply because what does the burner do? Heat it. Ethanol has a BP of somewhere around 78 degrees and the flame usually brings the temperature up enough so that the reaction doesn't take place until ethanol has entered the gaseous state.

Now, with the following information - don't take it as law; best ask Jake to confirm. As far as I know of, you should be treating propanol and below as a gas. But then once you reach butanol (with a BP of about 110 degrees according to Google) it won't matter too much. Yet, you really don't encounter the combustion of butanol and above that often. (The only time you do is where you have to compare the heat of combustion of alkanols in the experiment.)

[Kle123]

I have a question about a 'control experiment'. In trying to find an answer on the web, all that came up were things about controlled variables. To elaborate, the control experiment in which I'm not completely certain of its purpose is always seen in the discussion of a first hand experiment, addressing improvements in validity. E.g. in the acidic topic the experiment of decarbonating a carbonated drink through heating on a hotplate/boiling water bath is not completely valid. To improve validity a control of water is used.

Could you please explain to me what a control experiment is and its purpose. Thank you