Q15 / 150 · MHT CET 2026 (19 April Shift 2) · Chemistry
Chlorine has two isotopes $\text{Cl}^{37}$ and $\text{Cl}^{35}$ with percentage abundance of $25\%$ and $75\%$ respectively. Find average atomic mass of chlorine ?
- A$35$
- B$37$
- Correct answerC$35.5$
- D$36$
Solution
Average atomic mass is calculated using the formula:
$\text{Average atomic mass} = \dfrac{\sum (\text{Isotopic mass} \times \text{Percentage abundance})}{100}$
Substituting the given values:
$\text{Average atomic mass} = \dfrac{37 \times 25 + 35 \times 75}{100}$
$\text{Average atomic mass} = \dfrac{925 + 2625}{100}$
$\text{Average atomic mass} = \dfrac{3550}{100} = 35.5$
Answer: $35.5$
$\text{Average atomic mass} = \dfrac{\sum (\text{Isotopic mass} \times \text{Percentage abundance})}{100}$
Substituting the given values:
$\text{Average atomic mass} = \dfrac{37 \times 25 + 35 \times 75}{100}$
$\text{Average atomic mass} = \dfrac{925 + 2625}{100}$
$\text{Average atomic mass} = \dfrac{3550}{100} = 35.5$
Answer: $35.5$
Hence, the correct answer is option: 'C'.