VCE Chemistry Question Thread

[Sirius]

I've been struggling with equilibrium and I need serious help with this question. We're almost done with unit 4 area of study 1 in class and i'm still behind on these equilibrium questions. Please help!! 

In a reaction specified by the equation:
2A(g) ⇌ 2B(g) + C(g)
3.5 mol of substance A is initially introduced into
a 500 mL reaction vessel and allowed to reach
equilibrium. At this stage, its concentration was
found to be 2.0 M. Calculate the value of the
equilibrium constant for this reaction.

Use the ICE table to work out concentrations of the other species at equilibrium and then simply supply it in the equilibrium constant K.
Hope I'm correct  . (PS we just completed equilibrium as well)

[xghostariax]

Use the ICE table to work out concentrations of the other species at equilibrium and then simply supply it in the equilibrium constant K.
Hope I'm correct  . (PS we just completed equilibrium as well)

Thank you so much for you help, really appreciate it!!
Also you did get the answer correctly

[exit]

In the databook, is there any difference between using the heat of combustion value and the molar heat of combustion value to calculate energy released? Thanks, because they can turn out slightly different values.

[ardria]

How would you work out the oxidation numbers of Cu and S in the attached question?

Thank you 

[MisterNeo]

How would you work out the oxidation numbers of Cu and S in the attached question?

Thank you 

Hi! An easy method to find oxidation states is to write out the charges of each element component of the equation like what I have done here:

You can observe that a change in valency does occur with sulfur from 2- to 6+, but no change with copper.
Hope this answers your question

[ardria]

Hi! An easy method to find oxidation states is to write out the charges of each element component of the equation like what I have done here:
(Image removed from quote.)
You can observe that a change in valency does occur with sulfur from 2- to 6+, but no change with copper.
Hope this answers your question

Thank you so much! If i've understood that correctly...

You know that Cu in "CuS" is +2 because that's the charge on the Cu ion?

[MisterNeo]

Thank you so much! If i've understood that correctly...

You know that Cu in "CuS" is +2 because that's the charge on the Cu ion?

Yeah! Copper has two charges/valencies: 1+ and 2+.
You can tell if it is 1+ or 2+ by the empirical formula of copper sulfide in the equation.
Cuprous Sulfide (1+)

Cupric Sulfide (2+)

Sulfur has valencies of: 2-, 0, 2+, 4+, and 6+.
The equation gives CuS with a 1:1 ratio, thus copper is 2+ since it can only go with the 2- sulfur valency.
If it gave Cu2S, then that is 1+ copper with 2- sulfur.
Hope this clears things up

[simrat99]

Hey guys, I was wondering what would happen to CO2 emissions as you increase the size of alcohols undergoing combustion. Would more CO2 be produced or less CO2? Thanks

[Ahmad_A_1999]

Hey guys, I've utterly confused myself, what is the difference between having an equilibrium reaction and then writing the reverse? I know the Kc is the reciprocal but what does this reverse reaction even mean? And how is this achieved?

Thanks in advance

[AngelWings]

Hey guys, I've utterly confused myself, what is the difference between having an equilibrium reaction and then writing the reverse? I know the Kc is the reciprocal but what does this reverse reaction even mean? And how is this achieved?

Thanks in advance

I'd love to explain this in detail with you Ahmad_A_1999, but unfortunately I don't have much time right now. I think this will be a good beginning point for you to understand reverse reactions and then click some of the topics under "Mathematical Bits" for a bit more information. Those two links should answer your question.
Some other good sources here are: Khan Academy, Bozeman Science and Crash Course Chemistry for a more holistic approach. 

[Ahmad_A_1999]

I'd love to explain this in detail with you Ahmad_A_1999, but unfortunately I don't have much time right now. I think this will be a good beginning point for you to understand reverse reactions and then click some of the topics under "Mathematical Bits" for a bit more information. Those two links should answer your question.
Some other good sources here are: Khan Academy, Bozeman Science and Crash Course Chemistry for a more holistic approach. 

Thanks man! I'll be sure to have a look through all of them

[TFAnime123]

Can someone help me with Question 6? Thank you.

[Sine]

(Image removed from quote.)

Can someone help me with Question 6? Thank you.

The concentration of Ba2+ and SO42- are the same. The is because they have the same molar coefficients - hence same moles produced after BaSO4 dissolves - same concentration.

Does this help?

[exit]

In the databook, is there any difference between using the heat of combustion value and the molar heat of combustion value to calculate energy released? Thanks, because they can turn out slightly different values.

bump

[TFAnime123]

The concentration of Ba2+ and SO42- are the same. The is because they have the same molar coefficients - hence same moles produced after BaSO4 dissolves - same concentration.

Does this help?

I get that the concentrations of Ba2+ and SO42- are the same, but how do you do and show the calculations?