SCI 270: On Nuclear Technology Practice Problems
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## 2. Natural Units: electrons, atoms, molecules, and natural constants

1. Complete this Table for the properties of an electron:

Rest mass in J Rest mass in MeV g kg amu
8.1872e-14 0.5110 9.1094e-28 9.1094e-31 0.00054856

2. Complete this table for the electron

Charge in C Charge in esu Spin Magnetic moment
-1.6022e-19 -4.8066e-10 ½ 9.28477e-24 J T-1

3. Give some fundamental constants

 Charge for one mole of electron F = 96485.31 C Avogadro's number NA = 6.0221e23 particle mol-1 Give the formula and result you use to estimate the charge per electron from F F/NA = 1.6022e-19 C The Planck constant h = 6.62619e-34 J s-1

4. An electron has a kinetic energy of 1 eV. Give the following:

 Kinetic energy in J = 1.602197e-19 J (=C V) Velocity of the electron (2E/m)1/2 = 5.931e5 m/s

5. Estimate the Coulomb force of attraction when the electron is 53 pm (1 pm = 1e-12 m) from a proton.

 Force = 8.2158e-8 N (a small force) Note F = C q1 q2 / r2 C = 8.98755e9 N m2C-2 or F = q1 q2 / 4p eo r2 eo = 8.85e-12 N-1 m-2C2 p = 3.141592; Some browser cannot produce pi. q = e = 1.6022e-19 C

6. To decompose 36 g of water, 4 F charges must pass through the electrodes. If the voltage applied is 1.23 V, calculate the energy required for this decomposition.

 36 g water = 2 mol Number of molecules in 36 g water = 1.20442e24 molecules 2 NA Number of atoms in 36 g water = 3.61326e24 atoms 6 NA Energy = 2.962e21 keV 4 F * 1.23 Energy required to decompose a water molecule 2.46 eV 2*1.23 eV