At 25C, a mixture of NO2 and N2O4 gases are in equilibrium in a cylinder fitted with a movable piston. The concentrations are [NO2] 5 0.0475 M and [N2O4] 5 0.487 M. The volume of the gas mixture is halved by pushing down on the piston at constant temperature. Calculate the concentrations of the gases when equilibrium is reestablished. Will the color become darker or lighter after the change? [Hint: Kc for the dissociation of N2O4 to NO2 is 4.63 3 1023 . N2O4(g) is colorless and NO2(g) has a brown color.]
Energy levels The energy of each orbit is referred to as an energy level – allowed energies are often marked on an energy level diagram Note that the orbit energies are negative numbers. They indicate how low in energy the electron is relative to the free state (electron at infinite distance from the nucleus with no kinetic energy) The value of n, the so called principle quantum number, determines the energy Atomic spectra ▯ When atoms are excited by heating or in an electric discharge they emit light at discrete wavelengths ▯ When atoms are exposed to white light they only absorb certain wavelengths ▯ Both phenomena arise from transitions between different energy levels ▯ Atomic spectra
