Explanation:
For what I can see, is missing the concentration of [Ag+] in the half-cell. To calculate it:
Niquel half-cell
Oxidation reaction: 
![E=E^0 - \frac{R*T}{n*F}*ln(1/[Ni^{2+}])](https://tex.z-dn.net/?f=E%3DE%5E0%20-%20%5Cfrac%7BR%2AT%7D%7Bn%2AF%7D%2Aln%281%2F%5BNi%5E%7B2%2B%7D%5D%29)
Assuming T=298 K / R=8.314 J/mol K / F=96500 C
Silver half-cell
Reduction reaction: 
![E=E^0 - \frac{R*T}{n*F}*ln(1/[Ag+])](https://tex.z-dn.net/?f=E%3DE%5E0%20-%20%5Cfrac%7BR%2AT%7D%7Bn%2AF%7D%2Aln%281%2F%5BAg%2B%5D%29)
Assuming T=298 K / R=8.314 J/mol K / F=96500 C
![0.835V=0.8V - \frac{8.314*298}{1*96500}*ln(1/[Ag+])](https://tex.z-dn.net/?f=0.835V%3D0.8V%20-%20%5Cfrac%7B8.314%2A298%7D%7B1%2A96500%7D%2Aln%281%2F%5BAg%2B%5D%29)
![[Ag+]=0.26 M](https://tex.z-dn.net/?f=%5BAg%2B%5D%3D0.26%20M)
Answer:
See explanation
Explanation:
According to Avogadro's law, the volume of a given mass of gas is directly proportional to the number of molecules of gas present at constant temperature and pressure.
Hence; V1/n1 = V2/n2
The implication of this is, if there were X molecules present and the volume of the balloon is halved, the number of molecules of gas present is also halved. So, we now have X/2 number of gas molecules present in the balloon.
This is in accordance with the statement of Avogadro's law.
