Question

Use the de Broglie relationship to determine the wavelengths of the following objects.

1/ A lithium atom moving at 2.6×10⁵ m/s

Answer 1

molar mass of Li = 6.968 g/mol

This is mass of 6.022*10^23 atoms

we have below equation to be used:

mass of 1 atom = molar mass /(6.022*10^23)

mass of 1 atom = 6.968/(6.022*10^23)

mass of 1 atom = 1.155*10^-23 g

so, we have:

v = 2.66*10^5 m/s

mass, m = 1.155*10^-23 g

= 1.155*10^-26 kg [using conversion 1 Kg = 1000 g]

we have below equation to be used:

lambda = h / (m*v)

lambda = (6.626*10^-34) / (1.155*10^-26*2.66*10^5)

lambda = 2.2*10^-13 m

Answer: 2.2*10^-13 m