Question

X, Y and Z represent three electrodes $Al^{3+}/Al$, $Cu^{2+}/Cu$ and $Ag^{+}/Ag$ with $E^{\circ}$ values -1.66, 0.34 and 0.80 V respectively. The correct order of oxidising power of these three electrodes is

• A. $X>Y>Z$
• B. $Z>Y>X$
• C. $X=Y=Z$
• D. $Y>Z>X$

Hint:

More Positive $E^{\circ}$ = Stronger Oxidising Agent (likes to gain electrons). More Negative $E^{\circ}$ = Stronger Reducing Agent.

Answer 1

The Correct Option is B

Step 1: Recall reduction potential.
The standard reduction potential $E^{\circ}$ tells how much a species wants to gain electrons and be reduced.

Step 2: Link it to oxidising power.
A higher, more positive $E^{\circ}$ means a stronger pull for electrons, which means a stronger oxidising power.

Step 3: List the values.
X is $Al^{3+}/Al$ with $-1.66$ V, Y is $Cu^{2+}/Cu$ with $+0.34$ V, and Z is $Ag^+/Ag$ with $+0.80$ V.

Step 4: Compare the numbers.
Arrange from highest to lowest: $+0.80$ is the biggest, then $+0.34$, then $-1.66$ is the smallest.

Step 5: Convert to electrodes.
So in order of value, Z is highest, then Y, then X. \[ +0.80 > +0.34 > -1.66 \]

Step 6: State the order.
The order of oxidising power is therefore Z then Y then X. \[ \boxed{Z > Y > X} \]