2010 VCAA Chemistry U4 Suggested solutions

[stonecold]

Also Mao, for Section B - Question 2 - Part a iv; can you also say that "The experiment would been conducted under standard conditions"? I said this because the K value for lactic acid was used, and that value in the data booklet was based on standard conditions.

I said this too, anyone think it'd get marks?

This will certainly get marks.  It is a valid point.

Yeah that's what I said. Though I do suspect that they were looking for the answer which Mao gave. Certainly should get the marks though.

I put Mao's answer but I like this better 

FUELS CELLS ARE NOT F******* RECHARGABLE... YOU PUT REACTANTS IN TO KEEP IT RUNNING... YOU DONT CONVERT THE PRODUCTS BACK INTO THE REACTIONS SO ITS NOT RECHARGABLE..................... if your dad is a doctor please tell me where he works cos im not going to see him

I agree.  If VCAA dog us out of a mark on this Q then I'll be kinda pissed...especially after they've made it explicitly clear in examiners reports that fuel cells are not rechargeable.

[teags92]

catalyst for H2so4 is vanadium oxide NOT vanadium pentoxide....

[10weid]

catalyst for H2so4 is vanadium oxide NOT vanadium pentoxide....

theyre all acceptable.. if u have ever heard of the prefix 'pent' it denotes the number 5 - since 5 oxygen atoms are presnt in one mole of v2o5, pentoxide is technically correct.,

[10weid]

umm the assumption with regard to the lactic acid, is it acceptable to say that it is assumed that all of the lactic acid dissolves in the water? coz if it doesnt all dissolve, the calculation is incorrect..

[qshyrn]

are the standard conditions in the data booklet Ka values at 25 degrees C?

[qshyrn]

umm the assumption with regard to the lactic acid, is it acceptable to say that it is assumed that all of the lactic acid dissolves in the water? coz if it doesnt all dissolve, the calculation is incorrect..

nah dont think so. they asked u to find the percentage of ionization later on, so clearly theyre not gonna make u assume its 100 %

[mirra250]

umm the assumption with regard to the lactic acid, is it acceptable to say that it is assumed that all of the lactic acid dissolves in the water? coz if it doesnt all dissolve, the calculation is incorrect..

nah dont think so. they asked u to find the percentage of ionization later on, so clearly theyre not gonna make u assume its 100 %

that doesnt make sense qshryn..?
yes i think they will accept it 10weird

[10weid]

nooo, as in the 4.50grams of lactic acid all dissolved...

[10weid]

umm the assumption with regard to the lactic acid, is it acceptable to say that it is assumed that all of the lactic acid dissolves in the water? coz if it doesnt all dissolve, the calculation is incorrect..

nah dont think so. they asked u to find the percentage of ionization later on, so clearly theyre not gonna make u assume its 100 %

10weid* but thanks
that doesnt make sense qshryn..?
yes i think they will accept it 10weird

[qshyrn]

nooo, as in the 4.50grams of lactic acid all dissolved...

ooo ok.  are the Ka Values in the data book at 25degrees???   i wrote that i assumed the experiment was done at 25 degreres

[crayolé]

For the assumption question, "nothing reacts with the products to skew their concentration" would most likely be incorrect right?

[kakar0t]

would just Vanadium Oxide be accepted as an answer for 'name the catalyst' ?

[m@tty]

Yep.

[kakar0t]

Yep.

http://www.youtube.com/watch?v=GANY0T6Xkzk

[Potter]

Technically it should be Vanadium pentoxide of Vanadium(V) Oxide as there are different oxides of vanadium and these are oxides are not used as catalysts. However, I don't think VCAA will be that picky.. Never know though..