Rod's Chemistry 3/4 Questions Thread

[lzxnl]

Would a reasonable explanation for carbon-neutral be that there is no net increase in the CO2 levels in the atmosphere through the burning of these fuels?

VCAA would probably accept that

Why does the accumulation of charge in one half cell in the galvanic cell stop electricity from being produced?

That's because when charge is accumulated, you have an external electric potential that begins to counter the cell potential.
Also, it means you don't have a complete circuit.

[Rod]

VCAA would probably accept that

That's because when charge is accumulated, you have an external electric potential that begins to counter the cell potential.
Also, it means you don't have a complete circuit.

Stilll not making sense, it should though I do physics ;'(.

What do you mean by electrical potential countering the cell potential?

[PB]

I think what he means is that, the accumulation of electrons in one half of the galvanic cell would make it highly negative (obviously...haha). So that means that it is harder for electrons to flow in the circuit because the negativity would start to oppose and repel the incoming electrons.
I believe that is what he means by an external potential countering the cell potential.

[Rod]

I think what he means is that, the accumulation of electrons in one half of the galvanic cell would make it highly negative (obviously...haha). So that means that it is harder for electrons to flow in the circuit because the negativity would start to oppose and repel the incoming electrons.
I believe that is what he means by an external potential countering the cell potential.

Awesome, thank you PB

[Rod]

Just copying and pasting some of my notes. If highlighted WHY? next to some of my notes because I need a bit more info, and the textbook/internet has not really provided me that info.

All galvanic cells have two half cells, with each containing an electrode. The type of electrode we use depends on some factors. If one member of the electrode is a metal, then that particular metal itself is used the electrode. Why?


If there is no metal present, an inert electrode such as platinum or graphite is used. Why?


In some half cells, if one of the half cells is a gas, in this case a ‘special’ kind of electrode is used, and basically a glass tube is coated over the platinum or graphite electrode. Why?

cheers

[Rod]

Study design question:

For primary cells, do we need to specifically know

- dry cells
- alkaline cells
- button cells

And for secondary cells:

- car batteries
- nickle based batteries

Thank you!

[Rod]

Scrap the last question I asked, but still need a bit of help on the question I asked on the 7th of July.

But here's any easy one, help appreciated

Just with fuel cells, what makes them so good is that the waste products in fuel cells is always water. Unlike other cells such as galvanic cells, which produce ions like Pb2+ and Cu2+ etc. Why is it better to have water as a waste product than charged ions? Is it just so it's easier to remove?

And another question, the products from reactions of fuel cells start of as charged ions, like H+, how do these charges become water? Do they react to a specific electrolyte roaming around in the fuel cell? If so what electrolyte

thanks

[Rod]

Question 12
Consider the following statements about alkanes.
I Alkanes react with oxygen to produce carbon dioxide and water.
II Alkanes react with hydrogen chloride to produce chloroalkanes.
IIIAlkanes react with sodium hydroxide to produce alkanols.
Which of the statements above are true?
A. I only
B. I and II only
C. I and III only
D. I, II and III
Answer is A.
Worked solution
• A is correct because I is the only correct statement. Alkanes are a hydrocarbon and react with oxygen in a complete combustion reaction to produce carbon dioxide and water.
• B is incorrect because II is an incorrect statement. Alkanes must react with chlorine in a substitution reaction to produce chloroalkanes.
• C is incorrect because III is an incorrect statement. Alkanes react with water in a substitution reaction to produce alkanols.
• D is incorrect because II and III are incorrect statements. Alkanes must react with chlorine in a substitution reaction to produce chloroalkanes and react with water in a substitution reaction to produce alkanols.


Waah? Why doesn't INSIGHT consider the reaction between alkane + cl a reaction? Sure it's a substitution, but why can't it be a reaction?

[lzxnl]

Study design question:

For primary cells, do we need to specifically know

- dry cells
- alkaline cells
- button cells

And for secondary cells:

- car batteries
- nickle based batteries

Thank you!

I wasn't asked to know specific battery types for my year

Scrap the last question I asked, but still need a bit of help on the question I asked on the 7th of July.

But here's any easy one, help appreciated

Just with fuel cells, what makes them so good is that the waste products in fuel cells is always water. Unlike other cells such as galvanic cells, which produce ions like Pb2+ and Cu2+ etc. Why is it better to have water as a waste product than charged ions? Is it just so it's easier to remove?

And another question, the products from reactions of fuel cells start of as charged ions, like H+, how do these charges become water? Do they react to a specific electrolyte roaming around in the fuel cell? If so what electrolyte

thanks

Well...if you have charged ions as products, they may precipitate out of solution if their concentration goes too high. That's not a problem with the hydrogen oxygen fuel cell.

As for H+ becoming water, try the reaction O₂ + 4H⁺ + 4e^- => 2H₂O

Question 12
Consider the following statements about alkanes.
I Alkanes react with oxygen to produce carbon dioxide and water.
II Alkanes react with hydrogen chloride to produce chloroalkanes.
IIIAlkanes react with sodium hydroxide to produce alkanols.
Which of the statements above are true?
A. I only
B. I and II only
C. I and III only
D. I, II and III
Answer is A.
Worked solution
• A is correct because I is the only correct statement. Alkanes are a hydrocarbon and react with oxygen in a complete combustion reaction to produce carbon dioxide and water.
• B is incorrect because II is an incorrect statement. Alkanes must react with chlorine in a substitution reaction to produce chloroalkanes.
• C is incorrect because III is an incorrect statement. Alkanes react with water in a substitution reaction to produce alkanols.
• D is incorrect because II and III are incorrect statements. Alkanes must react with chlorine in a substitution reaction to produce chloroalkanes and react with water in a substitution reaction to produce alkanols.


Waah? Why doesn't INSIGHT consider the reaction between alkane + cl a reaction? Sure it's a substitution, but why can't it be a reaction?

Your question explains my disdain for the VCE chemistry course in not teaching detail. Alkanes react with elemental bimolecular chlorine in the presence of UV light because UV light breaks the Cl-Cl bond, producing two chlorine atoms with 7 valence electrons that are pretty damn reactive. As a result, these chlorine atoms are able to collide with alkane C-H bonds and break them.

Chloride, however, is pretty unreactive. It already has a stable octet of electrons, so why would it need to react?

Btw, the given answers are inaccurate. Alkanes don't react with water; the answers have confused alkanes with alkenes.

[Rod]

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Thank you so much!