Question

calculate the atomic mass of iridium, iridium has two isotopes. iridium-191 has a mass of 191.0 amu and a percent abundance of 37.58%. Iridium-193 has a mass of 193.0 amu and a percent abundance of 62.42%

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Answer 1

To calculate the atomic mass of iridium based on its isotopes, we need to consider the mass of each isotope and its percent abundance. The formula for calculating the atomic mass is as follows:

\[
\text{Atomic Mass} = (\text{mass of isotope 1} \times \text{fractional abundance of isotope 1}) + (\text{mass of isotope 2} \times \text{fractional abundance of isotope 2})
\]

### Step-by-Step Calculation

1. **Convert Percent Abundance to Fractional Abundance:**
- For Iridium-191:
\[
\text{Fractional Abundance} = \frac{37.58}{100} = 0.3758
\]
- For Iridium-193:
\[
\text{Fractional Abundance} = \frac{62.42}{100} = 0.6242
\]

2. **Multiply Mass by Fractional Abundance:**
- For Iridium-191:
\[
191.0 \, \text{amu} \times 0.3758 = 71.81 \, \text{amu}
\]
- For Iridium-193:
\[
193.0 \, \text{amu} \times 0.6242 = 120.03 \, \text{amu}
\]

3. **Add Both Contributions:**
\[
\text{Atomic Mass of Iridium} = 71.81 \, \text{amu} + 120.03 \, \text{amu} = 191.84 \, \text{amu}
\]

### Final Result
The atomic mass of iridium is approximately **191.84 amu**.