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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: matt123 on November 09, 2010, 01:23:51 pm

Title: VCAA MC QUESTION 18??? WTH?
Post by: matt123 on November 09, 2010, 01:23:51 pm
hey guys
http://www.vcaa.vic.edu.au/vcaa/vce/studies/chemistry/exams/2008/2008chem2-w.pdf
Question 18 multi choice

i cant understand why its D.
I get B???
reductants have LOWER voltage ? no??

So why shouldn't it be B?
Title: Re: VCAA MC QUESTION 18??? WTH?
Post by: toshibaj on November 09, 2010, 01:26:46 pm
put them in order of electrochemical series. i got pu2+ at top and R+ at bottom. Looking at the right side,the bottom one is the strongest reductant. Therefore when increasing reductant strength, start at the top, and go down.
Title: Re: VCAA MC QUESTION 18??? WTH?
Post by: matt123 on November 09, 2010, 01:29:26 pm
put them in order of electrochemical series. i got pu2+ at top and R+ at bottom. Looking at the right side,the bottom one is the strongest reductant. Therefore when increasing reductant strength, start at the top, and go down.

Mate
Cu has LOWEST voltage (0.46)
dosnt that make it the best reductant? ( lower voltage on electrochemical series = stronger reductant)
Title: Re: VCAA MC QUESTION 18??? WTH?
Post by: JinXi on November 09, 2010, 01:31:15 pm
Didn't need to use the electrochemical series.

Since we know that redox reactions occurs with a -ve gradient.

P > Cu , Cu> Q/R, Q> R,

Lay them out, then go from top to bottom for the right side.

Thats how i do it anyway. Hope it makes sense
Title: Re: VCAA MC QUESTION 18??? WTH?
Post by: jasoN- on November 09, 2010, 01:35:41 pm
these are potential voltages (ie. the difference)
We know that positive is cathode -> ie. reduction so.. (look at attached)
Title: Re: VCAA MC QUESTION 18??? WTH?
Post by: matt123 on November 09, 2010, 01:48:12 pm
these are potential voltages (ie. the difference)
We know that positive is cathode -> ie. reduction so.. (look at attached)

Yeah so they are oxidants
so looking at the table
we wanna look at the - terminal .. for the REDUCTANTS ..?

grrr this is so confusing lol
Title: Re: VCAA MC QUESTION 18??? WTH?
Post by: matt123 on November 09, 2010, 01:48:54 pm
wait dw
i think i get it now
thanks