Question

1. a sample of copper contains 69.2% of cu - 63 (62.929 amu) and 30.8% of cu - 65 (64.927 amu). calculate the average atomic mass of copper. round to two decimal places. copper average atomic mass amu

Explanation:

Step1: Convert percentages to decimals

$69.2\% = 0.692$, $30.8\%=0.308$

Step2: Use the formula for average atomic mass

The formula for average atomic mass $A = m_1x_1 + m_2x_2$, where $m_1$ and $m_2$ are the masses of the isotopes and $x_1$ and $x_2$ are their respective abundances.
$A=(62.929\times0.692)+(64.927\times0.308)$
$A = 62.929\times0.692+64.927\times0.308$
$A=43.546868 + 20.097516$
$A = 63.644384$

Step3: Round to two decimal places

Rounding $63.644384$ to two decimal places gives $63.64$

Answer:

$63.64$ amu