The wave length decreases
The answer is 80 atomic mass
In general, solubility increases with temperature. When you increase the temperature of a solvent, you increase the kinetic energy (or energy of movement) of the molecules, and this greater energy helps dissolve more of the solute molecules.
The answer for this issue is:
The chemical equation is: HBz + H2O <- - > H3O+ + Bz-
Ka = 6.4X10^-5 = [H3O+][Bz-]/[HBz]
Let x = [H3O+] = [Bz-], and [HBz] = 0.5 - x.
Accept that x is little contrasted with 0.5 M. At that point,
Ka = 6.4X10^-5 = x^2/0.5
x = [H3O+] = 5.6X10^-3 M
pH = 2.25
(x is without a doubt little contrasted with 0.5, so the presumption above was OK to make)