An electron in a hydrogen atom relaxes to the n = 4 level, emitting light of 114 THz. What is the value of n for the level in which the electron originated?

Solution (a)The balanced equation for the reaction between potassium and hydrogen is as given below 2K (s) 22 (g) (s) (b)Let us find the energy changes for the 2 reactions separately in order to compare them. The first reaction + - K (g) K (g) (g)H (g) can be split into the following 2 steps K K + +e -------eqn 1 ,energy required E =I.E=+419 KJ/mole (g) (g) 1 H (g)H -(g) -------eqn 2 ,enegy required E =E.A=-73KJ/2le Thus the net energy change required for the process will be sum of the energy changes for both reactions(E +E ) 1 2 =Ionisation energy of K+Electron gain enthalpy of H =+419 KJ/mole -73KJ/mole) =346 KJ/mole The second reaction is as given below K +H K - +H + (g) (g) (g) (g) Splitting it into 2 steps + - H (g) (g)e -------eqn 1,energy required E =I.E=+1312 KJ3ole - - K (g)K (g) --------eqn 2 ,enrgy required E =E.A=-48KJ4ole Thus the net energy change required for the process will be sum of the energy changes for both reactions(E +E ) 3 4 =Ionisation energy of H+Electron gain enthalpy of K =+1312 KJ/mole -48KJ/mole =1264KJ/mole