Concept:An atomic mass unit (amu) is incredibly small and is used to express the mass of subatomic particles and atoms. It can be directly converted into kilograms to bridge the microscopic and macroscopic realms.
Formula:$$ 1 \text{ a.m.u.} = \frac{1 \text{ gram}}{N_A} \div 1000 $$
Solution:- By definition, 1 amu is precisely \( \frac{1}{12} \) the mass of a single Carbon-12 atom.
- Mathematically, \( 1 \text{ amu} = 1 / (6.022 \times 10^{23}) \text{ grams} \).
- \( 1 \text{ amu} \approx 1.660539 \times 10^{-24} \text{ grams} \).
- To convert grams to kilograms, multiply by \( 10^{-3} \).
- \( (1.660539 \times 10^{-24}) \times 10^{-3} = 1.661 \times 10^{-27} \text{ kg} \).
Why other options are incorrect:- \( 0.666 \times 10^{-27}\text{kg} \): Incorrect mantissa.
- \( 1.661 \times 10^{28}\text{kg} \): Massive positive exponent, implying an atom weighs more than the Earth.
- Option D: (Distractor identical in source text, inherently wrong alongside C depending on selection).
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