Question

all copper in the world exists as two isotopes: 1) copper - 63, which has an abundance of 69.15% 2) copper - 65, which has an abundance of 30.85% calculate the average atomic mass of copper. round to two decimal places. (1 point)
128 amu
63.62 amu
64.00 amu
68.32 amu

Explanation:

Step1: Multiply copper - 63 mass by its abundance

$63\times0.6915 = 43.5645$

Step2: Multiply copper - 65 mass by its abundance

$65\times0.3085=20.0525$

Step3: Sum the results

$43.5645 + 20.0525=63.617\approx63.62$

Answer:

63.62 amu