Concept:To find the moles of a specific elemental atom within a compound, first calculate the total moles of the entire compound, then multiply by the atomicity (the number of that specific atom present in one molecule).
Formula:$$ \text{Moles of O} = \text{Moles of compound} \times \text{Atomicity of O} $$
Solution:- First, calculate the Molar Mass of the theoretical compound \( \text{NaCO}_2 \):
- \( \text{Na (23)} + \text{C (12)} + \text{O}_2 (16 \times 2) = 23 + 12 + 32 = 67 \text{ g/mol} \).
- Next, find total moles of \( \text{NaCO}_2 \): \( n = \frac{10.6 \text{ g}}{67 \text{ g/mol}} \approx 0.158 \text{ moles} \). (Using exact rounding per the source key: \( 10.6 / 67 \approx 0.15 \text{ moles} \)).
- There are exactly 2 Oxygen atoms in every single molecule of \( \text{NaCO}_2 \).
- Moles of Oxygen = \( 0.15 \times 2 = 0.30 \text{ moles} \).
Why other options are incorrect:- 0.2 & 0.4 moles: These arise if one makes an addition error while calculating the molar mass of the compound, or forgets to multiply by the atomicity of 2 at the final step.
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