Question

wilson, makyla dtal - ch - term 1 - unit 2 assessment 25 - 26 what is the atomic mass of silicon if 92.21% of its atoms have a mass of 27.977 amu, 4.70% have a mass of 28.976 amu, and 3.09% have a mass of 29.974 amu? round your answer to four significant digits and only include the number without the units for the answer. assume the units to be in amu.

Explanation:

Step1: Recall atomic - mass formula

The atomic mass ($A$) is calculated using the formula $A=\sum_{i}x_im_i$, where $x_i$ is the fractional abundance and $m_i$ is the mass of the isotope.

Step2: Convert percentages to fractions

$92.21\% = 0.9221$, $4.70\%=0.0470$, $3.09\% = 0.0309$.

Step3: Calculate atomic mass

$A=(0.9221\times27.977)+(0.0470\times28.976)+(0.0309\times29.974)$
$A = 0.9221\times27.977=25.692$ (first - term calculation)
$A = 0.0470\times28.976 = 1.362$ (second - term calculation)
$A = 0.0309\times29.974=0.926$ (third - term calculation)
$A=25.692 + 1.362+0.926$
$A = 27.98$.

Answer:

27.98