The element copper (Cu) has two naturally occurring isotopes, 63Cu and 65Cu, with an average atomic mass of 63.55 u. Copper is 69.17% 63Cu, and the atomic mass of 63Cu is 62.9296 u. Calculate the mass of 65Cu (in u).

The mass of 65Cu is 64.9419 u

Explanation:

Step 1: Data given

Copper has 2 naturally occurring isotopes, 63Cu and 65Cu, with an average atomic mass of 63.55 u.

⇒ 63Cu = 69.17 % = 62.9296 u

Step 2: Calculate mass of 65Cu

100 % 69.17% = 30.83%

63.55u = 0.6917*62.9296 + 0.3083X

X = 64.9419u

The mass of 65Cu is 64.9419 u

mass 65Cu = 19.59 u

Explanation:

∴ atomic mass Cu = 63.55 u

∴ atomic mass 63Cu = 62.9296 u

∴ 69.17% 63Cu = (mass 63Cu / mass Cu) * 100

⇒ 0.6917 = mass 63Cu / mass Cu

⇒ mass 63Cu = (63.55) (0.6917) = 43.958 u

∴ mass Cu = mass 63Cu + mass 65Cu

⇒ 63.55 u = 43.958 u + mass 65Cu

⇒ mass 65Cu = 63.55 u - 43.958 u

⇒ mass 65Cu = 19.59 u