ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Martoman on November 09, 2010, 06:53:06 pm

Title: TSFX 2010
Post by: Martoman on November 09, 2010, 06:53:06 pm
2B, why do they replace the NH2COONH4 with a value of 1? (lol to avoid a quadratic equation I think)
Title: Re: TSFX 2010
Post by: stonecold on November 09, 2010, 06:54:13 pm
Not having seen the Q, I don't know,  but if it is in a K equation, and is solid, solids are are assigned a conc of 1...
Title: Re: TSFX 2010
Post by: ghadz7 on November 09, 2010, 06:55:07 pm
I had the same issue! If they replaced it with one then the amount is already known! CONFUSION!
Title: Re: TSFX 2010
Post by: Martoman on November 09, 2010, 06:57:06 pm
Not having seen the Q, I don't know,  but if it is in a K equation, and is solid, solids are are assigned a conc of 1...

The FUDGE?

That would imply that since the equlibrium mole is 0.385-x then x = -1.615.... LOL

Since when do we assign them 1?
Title: Re: TSFX 2010
Post by: ghadz7 on November 09, 2010, 06:57:55 pm
Not having seen the Q, I don't know,  but if it is in a K equation, and is solid, solids are are assigned a conc of 1...

The FUDGE?

That would imply that since the equlibrium mole is 0.385-x then x = -1.615.... LOL

Since when do we assing them 1?

That's why I think TSFX exams are stupid! :P
Title: Re: TSFX 2010
Post by: stonecold on November 09, 2010, 06:58:26 pm
I haven't seen the Q, but solid species are assigned conc = 1.  It is a rule...

You basically just ignore them.
Title: Re: TSFX 2010
Post by: Martoman on November 09, 2010, 06:58:35 pm
but but but but q 6 was sex on a plate
Title: Re: TSFX 2010
Post by: Martoman on November 09, 2010, 06:59:12 pm
I haven't seen the Q, but solid species are assigned conc = 1.  It is a rule...

You basically just ignore them.

................lol............. its not in the textbook, lucky I found this out.
Title: Re: TSFX 2010
Post by: cameron_15 on November 09, 2010, 07:00:33 pm
A solid doesn't have a concentration...

Yep, I only found out thanks to KBT, very unusual question, hopefully we get it on Thursday, we'll be sweet!
Title: Re: TSFX 2010
Post by: Martoman on November 09, 2010, 07:02:07 pm
A solid doesn't have a concentration...

Yep, I only found out thanks to KBT, very unusual question, hopefully we get it on Thursday, we'll be sweet!

Yeah but thats just..... odd.
Title: Re: TSFX 2010
Post by: cameron_15 on November 09, 2010, 07:04:00 pm
A solid doesn't have a concentration...

Yep, I only found out thanks to KBT, very unusual question, hopefully we get it on Thursday, we'll be sweet!

Yeah but thats just..... odd.

I agree, I don't understand it, but I can apply it.

That's what VCE is about right? being able to answer questions on the exam correctly. lol.
Title: Re: TSFX 2010
Post by: stonecold on November 09, 2010, 07:05:34 pm
Is this exam worth doing?

Tomorrow I am doing VCAA 09 and NEAP 08.

What other exams are worth doing, if any?

I've done all the other NEAP/STAV  and some Insight/Lisachem and KBT

Title: Re: TSFX 2010
Post by: Blakhitman on November 09, 2010, 07:12:46 pm
haha I learnt that solid thingy from Khan academy :P
Title: Re: TSFX 2010
Post by: Mao on November 09, 2010, 07:15:23 pm
Daughter, I am disappoint. I mentioned it in here: http://vcenotes.com/forum/index.php/topic,29208.msg308165.html#msg308165

:P
Title: Re: TSFX 2010
Post by: Martoman on November 09, 2010, 07:17:22 pm
 :-[ i've disappoint you quite a lot these few days.... yeah it makes perfect sense now
Title: Re: TSFX 2010
Post by: scocliffe09 on November 09, 2010, 07:19:15 pm

Is this exam worth doing?


I think it is, because it illustrates some interesting points/ideas. Just don't take it to seriously if you do do it and don't let it affect your confidence. Irena writes so many questions that some of them can occasionally be a bit...off the mark.
Title: Re: TSFX 2010
Post by: Blakhitman on November 09, 2010, 07:20:20 pm
Gotta finish those tutes before Thursday Mao :P
Title: Re: TSFX 2010
Post by: Martoman on November 10, 2010, 12:56:11 am
gahhhh not 2010, 2008 exam

Platinum electrodes are suspended into a 500ml solution containing the following ions

Ag+, Cu2+, Al3+, Ni2+. If the current was passed through the cell at constant voltage of 1.4, the last metal to be depositied onto the cathode would be

Ag
Cu
Al
Ni


So obviously Al is not, its below water. I say nickel but they say: To deposit Ni, and EMF of 1.46 V is required.. where did they get this EMF from?

in short their answer is Cu
Title: Re: TSFX 2010
Post by: samiira on November 10, 2010, 02:09:29 am
gahhhh not 2010, 2008 exam

Platinum electrodes are suspended into a 500ml solution containing the following ions

Ag+, Cu2+, Al3+, Ni2+. If the current was passed through the cell at constant voltage of 1.4, the last metal to be depositied onto the cathode would be

Ag
Cu
Al
Ni


So obviously Al is not, its below water. I say nickel but they say: To deposit Ni, and EMF of 1.46 V is required.. where did they get this EMF from?

in short their answer is Cu

i tried to find a reason where they got 1.46 but i failed.. i dnno mayb question seems dodgy.. i wud say Ni aswell..
Title: Re: TSFX 2010
Post by: samiira on November 10, 2010, 02:12:40 am
btw is the emf calculated like this 0.8+0.34+0.23 ..??
Title: Re: TSFX 2010
Post by: Martoman on November 10, 2010, 02:28:08 am
I have no idea actually...
Title: Re: TSFX 2010
Post by: crayolé on November 10, 2010, 03:57:11 am
Does it come from
O2 + 4H+ + 4e- ---> 2H2O       +1.23V

Ni2+ + 2e- ---> Ni(s)              -0.23V

-.23 + (-1.23) = -1.46 V
Title: Re: TSFX 2010
Post by: Mao on November 10, 2010, 03:08:06 pm
Gotta finish those tutes before Thursday Mao :P

haha, yeah right... I will endeavour to finish those by next year. I totally underestimated how much work I had. I've finished two slabs of mother in the last 4 weeks. TWO SLABS. (48 cans, that's right)
Title: Re: TSFX 2010
Post by: Blakhitman on November 10, 2010, 03:09:31 pm
Mother is disgusting.
Title: Re: TSFX 2010
Post by: samiira on November 10, 2010, 03:10:48 pm
Mother is disgusting.

yeh i hate mother.. i am all for 'V' .
Title: Re: TSFX 2010
Post by: 98.40_for_sure on November 10, 2010, 03:17:13 pm
What's wrong with mother? just finished 2 slabs of V and 1 slab of mother right in time for exam period finish :D
Title: Re: TSFX 2010
Post by: Martoman on November 10, 2010, 03:55:03 pm
still don't really get this..

Similarly, if you have a voltage of 2V why can't water be deposited at the cathode of an electrolytic cell ala KBT tsmania jones question?
Title: Re: TSFX 2010
Post by: crayolé on November 10, 2010, 08:48:02 pm
I was always taught that  in order to power a non-spontaneous reaction, you're going to need higher voltage than the EMF of both.
For the Tassy Jones one, electrolysis of water requires 1.23 - (-0.83) = 2.06V for the non-spontaneous reaction to go ahead, any lower and its going to do shit all
Title: Re: TSFX 2010
Post by: 3Xamz on November 10, 2010, 08:51:18 pm
Does it come from
O2 + 4H+ + 4e- ---> 2H2O       +1.23V

Ni2+ + 2e- ---> Ni(s)              -0.23V

-.23 + (-1.23) = -1.46 V


It's -.23 - (-1.23) = 1.46v.

If you get a negative EMF then the reaction won't be spontaneous and you won't have current through it.