VCAA MC QUESTION 18??? WTH?

[matt123]

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?

[toshibaj]

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.

[matt123]

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)

[JinXi]

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

[jasoN-]

these are potential voltages (ie. the difference)
We know that positive is cathode -> ie. reduction so.. (look at attached)

[matt123]

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

[matt123]

wait dw
i think i get it now
thanks