2010 VCAA Chemistry U4 Suggested solutions

[10weid]

also pretty sure 8 is A, dilution decreases ocncentration of all ions - just because hydronium ion conc decresases doesnt necessarily mean OH- increases...

dilution increases OH concentration as there is a higher concentration of OH in water than in acid. Therefore, OH increases. BTW, unless temperature is changed, ANY change in one ion concentration is iversely proportional to the change in the other ion concentration in order to satisfy the [OH][H3O]=10^-14 rule.

but this is a solution of HCl, npt pure water, thus the Kw rule does not necessarily apply - i think... wtev, i know that if a base is diluted, OH- decreases, and if an acid is diltued, H+ is decreased.. so ill stick with my answer..

[mustafa]

Mai is right, vanadium (v) oxide is the same as vanadium pentoxide.

And seriously there is no need to correct him by stating H2's enthalpy as 268 instead of 289 or watever. Concept is the same

[mirra250]

16 is C. D is not balanced (2:3 oxygen atoms)

[98.40_for_sure]

also pretty sure 8 is A, dilution decreases ocncentration of all ions - just because hydronium ion conc decresases doesnt necessarily mean OH- increases...

Why not? I always thought if one increases, the other decreases.

Dilution decreases ALL concs... nuff said? you can't dilute parts of your solution. why is there even debate about this

[Mao]

yeah i think 4 is A

also isnt question 16 C instead of D?
D is not balanced (there are 2 oxygen molecules on the left and 3 on the right)

ur combustion reaction of benzoic is wrong as well..

yes. yes. yes. Fixed. Still trawling the thread for other mistakes. That's what I get for not reading the question or writing anything down.

[m@tty]

also pretty sure 8 is A, dilution decreases ocncentration of all ions - just because hydronium ion conc decresases doesnt necessarily mean OH- increases...

The concentration oh is greater in the water, thus when it is added to the acidic solution the overall concentration of increases.

Also, Vanadium Oxide is fine for catalyst instead of Vanadium Pentoxide.

[Souljette_93]

Mai is right, vanadium (v) oxide is the same as vanadium pentoxide.

And seriously there is no need to correct him by stating H2's enthalpy as 268 instead of 289 or watever. Concept is the same

Yeah it is, but he did ask to point out the mistakes. And plus it did stumped me at first..

[Mao]

also catalyst foro sulfuric is vanadium pentoxide..

That is the same as Vanadium (V) oxide

[10weid]

cool, sorry i just never eard it called oxide b4 :p

also, u reckon they'll cut mc19 outta the exam?

[akira88]

16 is C. D is not balanced (2:3 oxygen atoms)

Yeah the equation you gave isn't balanced...

[Souljette_93]

also pretty sure 8 is A, dilution decreases ocncentration of all ions - just because hydronium ion conc decresases doesnt necessarily mean OH- increases...

Why not? I always thought if one increases, the other decreases.

Dilution decreases ALL concs... nuff said? you can't dilute parts of your solution. why is there even debate about this

No debate, i want to know the right answer. And it also because that would mean  my whole concept it wrong.

[Mao]

and H2 combusts in the data book at 286 kJ/mol not 289...

Mao, there is an error in Q's 2.1.b ii) The combustion is -286 Kj/mol, not 289


Also for the chosen chemical only sulfuric acid is given   , wouldn't you know of Ammonia as well?

oops. fixing now.

I do know production of Ammonia, but not at the VCE level, so I'd have no idea what you guys know is what I think I know and what I think you know might be completely different to what you think I know about what I think you know. (Got it? )

[mustafa]

also pretty sure 8 is A, dilution decreases ocncentration of all ions - just because hydronium ion conc decresases doesnt necessarily mean OH- increases...

Why not? I always thought if one increases, the other decreases.

Dilution decreases ALL concs... nuff said? you can't dilute parts of your solution. why is there even debate about this

Jess Christ.....

Pure water has a higher concerration on OH ions than an acid. So when mixed, the end solution will have an overall increased concentration of OH.

Surely ppl dd not forget about the OH concentration in pure water.

Besides the concentration of H+ ions and the concentration of OH ions needs to multiply to give A fixed value at a fixed temperatre. Temp was fixed in question....

Therfore is concentration of H+ ions decreases concentration of OH ions must increase if temp is kept constant.

[VeryCrazyEdu.]

Why doesn't the Li+ move to the left?? I thought it would finish the 'circuit' by doing so....feel free to correct me :S

[m@tty]

cool, sorry i just never eard it called oxide b4 :p

also, u reckon they'll cut mc19 outta the exam?

Why would they do that?

The question was fine?..