VCE Chemistry Question Thread

[jazzaa36]

Needing urgent help with this problem,
27g of glucose is added to 150ml of 0.3m glucose. After dissolving the added glucose, water is added to a total volume of 250ml. Calculate the molarity of glucose in the final solution.

Thanks in advance   

[Shadowxo]

Needing urgent help with this problem,
27g of glucose is added to 150ml of 0.3m glucose. After dissolving the added glucose, water is added to a total volume of 250ml. Calculate the molarity of glucose in the final solution.

Thanks in advance   

c=n/V, so you need to find n and V. V is given as 250mL, so 0.250L
n(added)=m/M = 27/180    plus    n(initial)=cV = 0.3*0.150
n(total)= 27/180+0.3*0.150 mol
Rest is just putting the numbers in the calculator

[deStudent]

Hint:
C(s) + O2(g) -> CO2(g) is the equation
It gives you the mass of coal, and says carbon is 25% of it. So you know mass of carbon therefore you know the number of moles of carbon and CO2

Thanks, that makes it a lot easier.

Also, how did you know that was the equation for the combustion of coal? I thought combustion reactions had to produce co2 and h2o as their products?

[Syndicate]

Thanks, that makes it a lot easier.

Also, how did you know that was the equation for the combustion of coal? I thought combustion reactions had to produce co2 and h2o as their products?

Not necessarily. Only the combustion of hydrocarbon chains (from VCE chemistry) produces water and Co2 products, whereas Coal is basically amorphous carbon, which combusts to produce only CO2.

[vcestressed]

Hey,
Can someone please help me with this question...
The file is attached.
Thanks!

[Shadowxo]

Hey,
Can someone please help me with this question...
The file is attached.
Thanks!

Hi
So you know the mass of CuSO4, 5.55g, so you can calculate the number of moles - n=m/M
You also know the mass of water - 8.68-5.55g = 3.13g. You can calculate the number of moles - n=m/M
Then the ratio of n(H2O) to n(CuSO4) is n(H2O)/n(CuSO4), and that's the number of water molecules per CuSO4 molecule - the unknown x value.

Hope this helps

[vcestressed]

Hi
So you know the mass of CuSO4, 5.55g, so you can calculate the number of moles - n=m/M
You also know the mass of water - 8.68-5.55g = 3.13g. You can calculate the number of moles - n=m/M
Then the ratio of n(H2O) to n(CuSO4) is n(H2O)/n(CuSO4), and that's the number of water molecules per CuSO4 molecule - the unknown x value.

Hope this helps

Hey shadow,
Thanks for your help! You are so amazing!!!
Is this okay?
http://imgur.com/3xPqZbL
Thanks again.

[Shadowxo]

Hey shadow,
Thanks for your help! You are so amazing!!!
Is this okay?
http://imgur.com/3xPqZbL
Thanks again.

Yep, but just keep in mind significant figures (not sure if you'd need it much in this question though). Also the periodic table I used in chem had elements to 1 decimal place (eg 1.0), if that's the one you'll be using at the end of the year it may benefit you to practice using it
Good working

[tasmia]

hey guys, what could some possible errors in a fuel cell be? Thanks!

[keltingmeith]

hey guys, what could some possible errors in a fuel cell be? Thanks!

Errors? That's a bit of a weird word to use, so I'm going to assume you mean "problems" or "faults".

The first one is fairly obvious - you need some sort of fuel to keep it going. As a result, it may not be renewable, and by-products could be toxic, considering you probably can't recycle them.

[tasmia]

Errors? That's a bit of a weird word to use, so I'm going to assume you mean "problems" or "faults".

The first one is fairly obvious - you need some sort of fuel to keep it going. As a result, it may not be renewable, and by-products could be toxic, considering you probably can't recycle them.

ya errors :p I forgot to put more detail into it. What I meant was possible errors when doing a practical on fuel cells. Sorry!

[deStudent]

For this question http://m.imgur.com/a/M1GCG
Part h) Are we expected to know the colours of gases? I probably should've known this since it was in the theory of this chapter, but in general would VCAA ask a question like this and expect response describing the kind of colour change occurring?

Also, when the concentration of the reactants and products (in the graph) are the same, is this meaningful in any way?

[Shadowxo]

For this question http://m.imgur.com/a/M1GCG
Part h) Are we expected to know the colours of gases? I probably should've known this since it was in the theory of this chapter, but in general would VCAA ask a question like this and expect response describing the kind of colour change occurring?

Also, when the concentration of the reactants and products (in the graph) are the same, is this meaningful in any way?

VCAA would only ask a question regarding colour changes if they told you the colours of the gases - like they stated at the beginning of this question. They wouldn't expect you to remember colours of gases/liquids etc off by heart.
The concentrations being equal just means the concentrations being equal - they could ask you when the concentrations were equal but it would hold little significance. The most important things are when the concentrations are unchanging (equilibrium), or when rate of forward + backwards reaction are equal (also equilibrium, but different graph).

[zxcvbnm18]

Do a lot of schools use qat for their sacs?

[deStudent]

Do a lot of schools use qat for their sacs?

Don't think so, from my experience QATs are probably one of the worst companies that make practice SACs.
--
Thanks Shadowxo for the reply.