/0's Chem Questions

[/0]

I remember dealing with this question last year..

The 'mould' only contains iron oxide and aluminium, no H+. Hence your answer wouldn't be accepted [however, VCAA wouldn't put this question on an exam anyways]

In this case, Iron (III) is reduced to elemental iron, and elemental aluminium is oxidised to Al³⁺, i.e. the oxides changed owners, while energy was released.

Thanks mao. I certainly hope that doesn't appear in an exam If we had Al(III) and Iron 'reacting' instead, would there be no reaction?

[Mao]

no there wouldn't be, according to the electrochemical series [which you will learn in more detail in U4]

[/0]

Why are not used as primary standards?

[TrueTears]

The common strong acids and bases can not be made directly into standard solutions.

Bases such as NaOH, LiOH and KOH are usually impure as they absorb water and react with carbon dioxide in the air, hence it is hard to get an accurate concentration of these. Also concentrations of commercial supplies of HCl, are not accurately specified.

[/0]

Thanks TT,

The amount of calcium carbonate () in the ore dolomite can be determined by gravimetric analysis. The dolomite sample is dissolved in acid and the calcium ions () are precipitated as calcium oxalate (). The calcium oxalate is filtered, dried and strongly heated to form calcium oxide ().

How do you find the equation for the reaction?

[Chemkid]

You dont: you just use mole ratios. The number of mole of CaO will be equal ro the number of mole of CaCO3.

[TrueTears]

[/0]

You dont: you just use mole ratios. The number of mole of CaO will be equal ro the number of mole of CaCO3.

oh is that because the amount of Ca must be conserved?

[TrueTears]

You dont: you just use mole ratios. The number of mole of CaO will be equal ro the number of mole of CaCO3.

oh is that because the amount of Ca must be conserved?

One would assume so.

[/0]

OK Thanks TT and chemkid!

[/0]

Calculate the percentage yield if 5.0 g of ethanol is oxidised to produce 4.8 g of ethanoic acid.

I got 73.6% but answers go 92%






How many peaks is that bolded H split into in proton NMR? Book says 1  peak wdf....

[TrueTears]

The answers are wrong for the first question. I remember dekoyl asking about this in the holidays as well.

Should be 12 peaks. (3+1)(2+1) = 12

Answers probs left out the 2.

[NE2000]

The answers are wrong for the first question. I remember dekoyl asking about this in the holidays as well.

Should be 12 peaks. (3+1)(2+1) = 12

Answers probs left out the 2.

Hmmm...with the multiplicity that creates 12 peaks, does VCAA operate like that or is it just Scotch ()? I've seen a few trial papers now that has CH3CH2CH2 generating 6 peaks (5+1) rather than 12 and I don't think any textbooks have multiplicity in there although I've seen it in uni textbooks (so obviously it exists and they are just trying to hide it from us). Apparently its even more complicated than just multiplying the two n+1s if you want to get properly accurate.

So does your textbook teach you about multiplying the peaks? Which is why the book would have left out the 2 from 12 to produce the clearly incorrect 1? What book is this?

[TrueTears]

The answers are wrong for the first question. I remember dekoyl asking about this in the holidays as well.

Should be 12 peaks. (3+1)(2+1) = 12

Answers probs left out the 2.

Hmmm...with the multiplicity that creates 12 peaks, does VCAA operate like that or is it just Scotch ()? I've seen a few trial papers now that has CH3CH2CH2 generating 6 peaks (5+1) rather than 12 and I don't think any textbooks have multiplicity in there although I've seen it in uni textbooks (so obviously it exists and they are just trying to hide it from us). Apparently its even more complicated than just multiplying the two n+1s if you want to get properly accurate.

So does your textbook teach you about multiplying the peaks? Which is why the book would have left out the 2 from 12 to produce the clearly incorrect 1? What book is this?

Nah, our teacher explicitly taught us about spin-spin coupling which only occurs if the adjacent hydrogen environments are different.

[dekoyl]

Sorry to hijack your thread, /0.

But interesting multiplying thing, TT. Are we expected to know this? I haven't heard anyone talk about this multiplicity.
If this turned up on the exam, I would've just wrote 6 peaks. =(