Calculate the atomic mass for copper using the weighted average mass method. Express your answer using two decimal places and include the appropriate units.

63. 55 amu

Explanation:

Copper is known to exist in two different isotopes which are Cu-63 and Cu-65.

Cu-63 has an atomic mass of 62.93 amu and it has an abundance of 69.15%.

Similarly,

Cu-65 has an atomic mass of 64.93 amu and it has an abundance of 30.85%

Therefore, using the weighted average mass method, the atomic mass of copper is:

Atomic mass of copper = (0.6915*62.93) amu + (0.3085*64.93) amu = 43.52 amu + 20.03 amu = 63.55 amu

Thus, the atomic mass of copper (express in two decimal places) is 63.55 amu