Air is mainly composed of N2 (78%), O2 (21%) and other trace gases. Now, the total pressure of air is the sum of the partial pressures of the constituent gases. The partial pressure of each gas, for example say O2, can be expressed as:
p(O2) = mole fraction of O2 * P(total, air) ----(1)
Thus, the partial pressure is directly proportional to the total pressure. If we consider a sealed container then, as the temperature of air increases so will its pressure. Based on equation (1) an increase in the pressure of air should also increase the partial pressure of oxygen.
For the silver nitrate test, the solution is added first with nitric acid. This test is to determine halide ions. When silver nitrate is added to the solution, the color of the precipitate would indicate the identity of the ion. For chloride ions, the precipitate is white.
For the sodium thiosulfate test, chlorine is treated with Ki solution which turns brown. When it is titrated with sodium thiosulfate solution, the brown turns yellow upon which, starch is added. It forms a complex which appears as dark blue. Upon adding more titrant, it reaches the endpoint where the blue turns colorless.
City B is at a higher temperature because as you go higher in altitude the boiling point of water becomes lower.
