Question

Two isotopes of an elements $Q$ are $Q^{97}$ (23.4% abundance) and $Q^{94}$ (76.6% abundance). $Q^{97}$ is $8.082$ times heavier than $C^{12}$ and $Q^{94}$ is $7.833$ times heavier than is $C^{12}$. What is the average atomic weight of the elements $Q$?

• A. $94.702$
• B. $78.913$
• C. $96.298$
• D. $94.695$

Answer 1

The correct option is A $94.702$

Average mass $=\frac{\text{Abundance of}{Q}^{97}\times \text{mass of}{Q}^{97}\times \text{Abundance of}{Q}^{94}\times \text{mass of}{Q}^{94}}{100}$

$=\frac{23.4\times 8.082\times 12+76.6\times 7.833\times 12}{100}$

$=94.702$ Answer.