VCE Chemistry Question Thread

[larissaaa_]

Hi larissaaa_!
The time you would use is the time you have the power source connected to the water  (e.g. in my case it was 3 minutes).
To calculate the calibration factor, you would go  CF=Energy (calculated by E=V*I*t) divided by the change in temperature in the given time frame.

Good luck with the SAC and I hope this helps!

Thank you so much! So there would t be a calibration factor value for after the power source has been turned off?

[HasibA]

do we need to know the specific electrolytic cells? i.e 28.5 onward from the heinemann book thanks!! eg like learning a down cell

[Sine]

do we need to know the specific electrolytic cells? i.e 28.5 onward from the heinemann book thanks!! eg like learning a down cell

You won't have to know them specifically but a understanding of them is probably good to have.

[Adequace]

Is anything about Ocean Acidity important for U3&4 chem? Thanks

[HasibA]

Is anything about Ocean Acidity important for U3&4 chem? Thanks

doing the old course, but the new course is fairly similar i think - pretty sure me and my class skipped most of the ocean, environment things and yeah never popped up in exams/sacs thus far, so i'd say its not that important (but others can validate what i say)

[sweetiepi]

Is anything about Ocean Acidity important for U3&4 chem? Thanks

doing the old course, but the new course is fairly similar i think - pretty sure me and my class skipped most of the ocean, environment things and yeah never popped up in exams/sacs thus far, so i'd say its not that important (but others can validate what i say)

Not sure about the new SD, but I haven't touched on anything like that in 3/4.

[jyce]

Is anything about Ocean Acidity important for U3&4 chem? Thanks

No, ocean acidity is not important for the new Units 3 and 4 SS being implemented next year 

[HasibA]

do we have to know the products of combustion for things other than hydrocarbons? i.e the combustion of just hydrogen gas appeared on a exam q

[Sine]

do we have to know the products of combustion for things other than hydrocarbons? i.e the combustion of just hydrogen gas appeared on a exam q

Yes you need to know combustion of most organic compounds (just react with O2 and balance). You only need to know complete combustion with products of water and carbon dioxide. We can't do equations for incomplete combustion since we can't predict products accurately.

[Elizawei]

Hey guys, got another quick question.

how much water must be added to a 1.0L strong base solution of pH 13.9 in order to decrease the pH to 12?

For this question, [H3O+]= 10^-13.9 right? or not
Because when i use c1v1 = c2v2, i get a smaller volume than the original, which is surely incorrect

Thanks in advance!

[sweetcheeks]

Hey guys, got another quick question.

how much water must be added to a 1.0L strong base solution of pH 13.9 in order to decrease the pH to 12?

For this question, [H3O+]= 10^-13.9 right? or not
Because when i use c1v1 = c2v2, i get a smaller volume than the original, which is surely incorrect

Thanks in advance!

Set the equation like this [OH-][H+]=10^-14
[OH-]=10^-14/10^-13.9
this gives the OH- concentration as 10^-0.1
We want the final concentration to be 10^-2 mole per litre (10^-14
/10¹² = 10^-2
Set up the equation CiVi=CfVf
10^-0.1 x1L=10^-2 xVf
solving for Vf gives us 79.4 litres total final concentration 79.4-1.0L gives us 78.4 Litres or 78Litres of water

[Elizawei]

thanks !

[smiley123]

I'll be doing an electroplating experiment tomorrow, and reading through the method there is a step:Connect your nickel/tin to the DC power’s negative terminal via the ammeter, and then the copper to the negative terminal.
What does this mean? Both electrodes are connected to the negative terminal? I'm really confused, please explain this to me. Thank you!

[sweetcheeks]

I'll be doing an electroplating experiment tomorrow, and reading through the method there is a step:Connect your nickel/tin to the DC power’s negative terminal via the ammeter, and then the copper to the negative terminal.
What does this mean? Both electrodes are connected to the negative terminal? I'm really confused, please explain this to me. Thank you!

The tin/nickel electrode should be connected to the cathode (negative electrode) and copper connected to the anode (positive electrode). You are trying to coat the tin/nickel in copper. You will use a copper solution (probably copper (II) sulfate). As power is supplied, the Cu2+ in the solution will be reduced to form Cu metal on the tin/nickel. The copper anode will be oxidized to replenish the Cu2+ that is being reduced.

[sweetiepi]

The tin/nickel electrode should be connected to the cathode (negative electrode) and copper connected to the anode (positive electrode). You are trying to coat the tin/nickel in copper. You will use a copper solution (probably copper (II) sulfate). As power is supplied, the Cu2+ in the solution will be reduced to form Cu metal on the tin/nickel. The copper anode will be oxidized to replenish the Cu2+ that is being reduced.

Correct me if I'm wrong, but isn't a cathode the positive electrode and the anode the negative electrode?