Atomic Mass Unit — Prelims Strategy

Prelims Strategy

For NEET questions on Atomic Mass Unit, a clear understanding of its definition, standard, and conversion factors is paramount. First, memorize the definition: 1 amu is 1/12th the mass of a carbon-12 atom.

Understand why carbon-12 was chosen. Second, know the conversion factor: $1\,\text{amu} \approx 1.6605 \times 10^{-24},\text{g}$. Third, internalize the crucial relationship: atomic mass in amu is numerically equal to molar mass in g/mol.

For numerical problems, always pay attention to the units requested (amu vs. grams) and whether the question asks for the mass of a single atom or a mole of atoms. When calculating average atomic mass, remember to use fractional abundances (percentage/100) and sum the products of (isotopic mass $\times$ fractional abundance).

For conceptual questions, be wary of trap options that refer to older definitions (like oxygen-16) or confuse relative mass with absolute mass. Practice converting between amu and grams, and calculating molecular/formula masses.

Double-check calculations, especially powers of ten and decimal places, as these are common sources of error in NEET.