Balance each one by adding electrons to make the charges on both sides the same:
Sn--> Sn2+ + 2 e-
Ag+ + 1 e- --> Ag
Now, you have to have the same number of electrons in the two half-reactions, so multiply the second one by 2 to get:
2 Ag+ + 2 e- --> 2 Ag
Now, just add the two half reactions together, cancelling anything that's the same on both sides:
2 Ag+ + Sn --> Sn2+ + 2 Ag
And you're done.
For this system, we use Dalton's law of partial pressures where the total pressure of a gas mixture is said to be equal to the sum of the partial pressures of the gases. The partial pressure of each gas would be calculated by the product of the mole fraction and the original pressure of the gas. We do as follows:
Total pressure = x1P1 + x2P2
Total pressure = (2.0 / 7.0 )(3.5) + (1.5/7.0)(2.6)
Total pressure = 1.56 atm
Atoms return to their ground state by emitting a photon of light.
