Question

Ionization is the removal of an electron to form a cation. It is possible to determine the ionization energy for hydrogen using the Bohr equation, making the assumption that ionization is the transition from n=1 to n=∞. How much energy (in kJ) is required to ionize 1 mole of hydrogen atoms? A. 2.18 x 10-18 J B. 4.72 x 103 J C. 1.66 x 103 J D. 1.31 x 103 J E. 5.72 x 103 J ______ Answer: D

7. Calculate the kinetic energy of the photoelectron emitted by a metal (threshold energy is 1.50 x 10-19 J) exposed to light of wavelength 5.00 x 10-7 m (the energy beyond that required to knock electron goes into electron kinetic energy). A. -3.98 x 10-19 J B. 3.98 x 10-19 J C. 2.48 x 10-19 J D. 1.50 x 10-19 J E. 8.3141 J ______ Answer: C

can you please explain the steps to get the answer. I have the answers but i dont now how to get them.

Answer 1

Delta elementof_(infinity, 1) = (-13.6/n_infinity^2) - (-13.6/1^2) = + 13.6/1 ev = 13.6 times 1.6 times 10^-19 = 2.58 times 10^-18 J For 1 mole = 2.58 times 10^-18 times 6.022 times 10^23 = 1.31 times 10^6 J or 1.3 times 10^3 K J Therefore (D option) (2) For photo electric effect h gamma = h gamma^0 + 1/2 mv^2 Total energy Threshold energy kinetic energy h nu = h c/lambda 1/2 mv^2 = h nu - h gamma^0 k. elementof = 6.6 times 10^-34 times 3 times 10^8/5 times 10^-7 - 1.5 times 10^-19 K. elementof 2.48 times 10^-19 J Therefore (C option)