Question

Convert the atomic mass of an oxygen atom to units of
MeV/c². (a) 1.88 x 10⁴ MeV/c² (b) 2.47 x 10⁴ MeV/c²
(c) 7.37 x 10³ MeV/c² (d) 9.21 x 10⁵ MeV/c² (e) 1.49 x
10⁴ MeV/c²

Please show how you got the correct answer. Thank you!

Answer 1

Lets find the value of 1 MeV/c² in kilogram first

e = 1.602*10^-19 C ( charge on 1 electron)

1 MeV in joules = 10⁶ * 1.602*10^-19 = 1.602*10^-13 Joules

c is 3*10⁸ m/s ( speed of light in vacuum)

1 MeV / c² = 1.602*10^-13 / (3*10⁸)² = 1.78 *10^-30 kg

Mass of 1 mole O atoms is 16*10^-3 kg

1 mole has 6.022*10²³ atoms

==> mass of 1 atom in kg = 16*10^-3 kg /  6.022*10²³ atoms = 2.6569 * 10^-26 kg

So mass of 1 atom in MeV/c² = 2.6569 * 10^-26 kg /  1.78 *10^-30 kg = 1.4926*10⁴ MeV/c²