VCE Chemistry Question Thread

[Bri MT]

Iron is given to 3 sig.fig. in the data book. Therefore your answer should be 3 sig.fig. The answer is 3.81% if you use 3.07g or 3.82% if you use 3.0745g. I prefer 3.07 and 3.81% because of the accuracy thing. I'm leaning towards them accepting either, and I think that's what they meant when they bolded both numbers.

I get where you're coming from here,  but I would generally advise that calculations are completed from calculator memory (ie not rounded) and that you round/apply sig figs for reporting answers.

If you round along the way for your calculations you lose accuracy, but I agree that in this case it seems like they were accepting both

[f0od]

Hi there, I don't really understand the answer to this question

- Describe the effect on the pH of a monoprotic acid solution of pH 0.1 when it is diluted by a factor of 10
The answer is: the pH is increased by one unit, but I'm not sure what it means or how to figure that out

Any help is greatly appreciated!

[Yertle the Turtle]

Hi there, I don't really understand the answer to this question

- Describe the effect on the pH of a monoprotic acid solution of pH 0.1 when it is diluted by a factor of 10
The answer is: the pH is increased by one unit, but I'm not sure what it means or how to figure that out

Any help is greatly appreciated!

In this case you use the pH formula: -log₁₀[H⁺] When you change the concentrations in this formula with a dilution, you can see the change in pH that occurs.

First you would find the initial concentration of H⁺ ions, and therefore of the acid since it is a monoprotic (single H⁺ ion). Then you use c1V1=c2V2 with a dilation factor of 10 to find c2, and then substitute that back into the pH formula to see the new pH.

[Lear]

is this part of the study design mate?

For Chemistry 1/2, pretty sure it is.

[A TART]

This has probably been asked before, but I can't find it on the forums.

Will we be penalised for writing instead of ??

[sweetiepi]

This has probably been asked before, but I can't find it on the forums.

Will we be penalised for writing instead of ??

The standard is writing \(\ce{Cu^{2+}}\). I have never heard of someone being penalised for writing it as +2, however I'd play it safe and always write it in standard format.

[Azim.m]

Even though sulfate is generally a spectator ion, why are there instances where they migrate to the positive electrode? Does this always happen even if they’re spectator ions?

[Yertle the Turtle]

This has probably been asked before, but I can't find it on the forums.

Will we be penalised for writing instead of ??

2+ is the standard for charges, while +2 is what you would use for oxidation numbers. There are cases, I believe, where this will actually be penalised, I think it has happened in one of my Chem SACs, and I guess it's always important to consider notation, as you never know when the chief examiner will be picky.

[Seno72]

Hey guys. Quick question, are the reactions in galvanic cells always exothermic/endothermic or can they be both?

[hums_student]

Hi guys, two quick questions -

1, How do TSSM, QATS, and NEAP trial exams compare to the VCAA ones in terms of difficulty?

2, I'm ranked in the top 10% in a below-average cohort. Roughly what score would be needed for a raw 37+ study score? (say, using the 2017 VCAA exam as an example?)

Thanks in advance.

[Sine]

Hi guys, two quick questions -

1, How do TSSM, QATS, and NEAP trial exams compare to the VCAA ones in terms of difficulty?

2, I'm ranked in the top 10% in a below-average cohort. Roughly what score would be needed for a raw 37+ study score? (say, using the 2017 VCAA exam as an example?)

Thanks in advance.

1. probably in the same ballpark as VCAA but from memory NEAP can have some tough questions and QATs and TSSM were on the easier side.

2. Aim for an A+ on the exam (generally this will yield you a 40 but in case sacs bring you down you could still get your aim).

[minhalgill]

theres 4 half equations with water in the electrochemical series. how do we know which one to use?

[minhalgill]

does anyone know how to do this?
whats the reaction of ch4 and h20?

[hums_student]

theres 4 half equations with water in the electrochemical series. how do we know which one to use?

I think a general rule of thumb is to not use the one with peroxide unless specified, and as for the other three it depends on if the condition is basic or acidic.
I'm not 100% sure about this though, so please correct me if I'm wrong
Also have my own question:
Are Cr2O7 and K2Cr2O7 the same thing? I feel like the obvious answer is no, seeing one has potassium and the other doesn't, but I see them used interchangeably in questions (see pic)


Thank you!

[Lear]

I think a general rule of thumb is to not use the one with peroxide unless specified, and as for the other three it depends on if the condition is basic or acidic.
I'm not 100% sure about this though, so please correct me if I'm wrong
Also have my own question:
Are Cr2O7 and K2Cr2O7 the same thing? I feel like the obvious answer is no, seeing one has potassium and the other doesn't, but I see them used interchangeably in questions (see pic)
(Image removed from quote.)

Thank you!

Potassium is typically a spectator ion and is not involved in the reaction. Therefore you may see K2Cr2O7 without the K2