The following information refers to the isotopes of copper and was collected by using a mass spectrometer - VCE - SSCE Chemistry - Question 3 - 2006 - Paper 1

Let the percentage abundance of $^{63}\text{Cu}$ be denoted as x%. Then the percentage abundance of $^{65}\text{Cu}$ would be (100 - x)%. Using the formula for relative atomic mass based on isotopes:

$ext{Relative Atomic Mass} = \frac{x}{100} \times 62.93 + \frac{100 - x}{100} \times 64.93$

Substituting the known relative atomic mass of copper (63.54):

$63.54 = \frac{x}{100} \times 62.93 + \frac{100 - x}{100} \times 64.93$

This simplifies to:

$63.54 = 0.6293x + 0.6493(100 - x)$

To solve for x, expand and collect like terms:

$63.54 = 0.6293x + 64.93 - 0.6493x$

Combine the x terms:

$63.54 - 64.93 = -0.0200x$

This leads to:

x = \frac{1.39}{0.0200} = 69.5\%$$ Thus, the percentage abundance of $^{63}\text{Cu}$ is approximately 69.5%.