Question

1. the natural isotope abundance of sulfur is shown on the table. what is the average atomic mass of sulfur? isotope sulfur-32 sulfur-33 sulfur-34 sulfur-36 percent abundance 95.0% 0.75% 4.21% 0.025% 32.09 amu 32.17 amu 32.98 amu 33.75 amu

Explanation:

Step1: Recall average - atomic - mass formula

The formula for average atomic mass $A = \sum_{i}m_i\times p_i$, where $m_i$ is the mass of the isotope and $p_i$ is the percent - abundance of the isotope (expressed as a decimal).

Step2: Convert percent - abundances to decimals

For sulfur - 32: $p_1=0.9500$, for sulfur - 33: $p_2 = 0.0075$, for sulfur - 34: $p_3=0.0421$, for sulfur - 36: $p_4 = 0.00025$. The masses of the isotopes are $m_1 = 32$, $m_2=33$, $m_3 = 34$, $m_4=36$.

Step3: Calculate the contribution of each isotope

Contribution of sulfur - 32: $m_1\times p_1=32\times0.9500 = 30.4$.
Contribution of sulfur - 33: $m_2\times p_2=33\times0.0075 = 0.2475$.
Contribution of sulfur - 34: $m_3\times p_3=34\times0.0421 = 1.4314$.
Contribution of sulfur - 36: $m_4\times p_4=36\times0.00025 = 0.009$.

Step4: Sum up the contributions

$A=30.4 + 0.2475+1.4314 + 0.009=32.0879\approx32.09$ amu.

Answer:

32.09 amu