<u>Answer:</u> The concentration of
in the solution is 
<u>Explanation:</u>
The given cell is:

Half reactions for the given cell follows:
<u>Oxidation half reaction:</u>
( × 3)
<u>Reduction half reaction:</u>
( × 2)
<u>Net reaction:</u> 
Substance getting oxidized always act as anode and the one getting reduced always act as cathode.
To calculate the
of the reaction, we use the equation:

Putting values in above equation, we get:

To calculate the concentration of ion for given EMF of the cell, we use the Nernst equation, which is:
![E_{cell}=E^o_{cell}-\frac{0.059}{n}\log \frac{[H^{+}]^6}{[Au^{3+}]^2}](https://tex.z-dn.net/?f=E_%7Bcell%7D%3DE%5Eo_%7Bcell%7D-%5Cfrac%7B0.059%7D%7Bn%7D%5Clog%20%5Cfrac%7B%5BH%5E%7B%2B%7D%5D%5E6%7D%7B%5BAu%5E%7B3%2B%7D%5D%5E2%7D)
where,
= electrode potential of the cell = 1.23 V
= standard electrode potential of the cell = +1.50 V
n = number of electrons exchanged = 6
![[Au^{3+}]=?M](https://tex.z-dn.net/?f=%5BAu%5E%7B3%2B%7D%5D%3D%3FM)
![[H^{+}]=1.0M](https://tex.z-dn.net/?f=%5BH%5E%7B%2B%7D%5D%3D1.0M)
Putting values in above equation, we get:
![1.23=1.50-\frac{0.059}{6}\times \log(\frac{(1.0)^6}{[Au^{3+}]^2})](https://tex.z-dn.net/?f=1.23%3D1.50-%5Cfrac%7B0.059%7D%7B6%7D%5Ctimes%20%5Clog%28%5Cfrac%7B%281.0%29%5E6%7D%7B%5BAu%5E%7B3%2B%7D%5D%5E2%7D%29)
![[Au^{3+}]=1.87\times 10^{-14}M](https://tex.z-dn.net/?f=%5BAu%5E%7B3%2B%7D%5D%3D1.87%5Ctimes%2010%5E%7B-14%7DM)
Hence, the concentration of
in the solution is 