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Question Q132) An element, X has the following isotopic composition 200X : 90% ; 199X : 8%; 202X : 2.0%.
The weighted average atomic mass of the naturally occurring element X is closest to


Using formula for average atomic mass
Average mass=(200×90+199×8+202×2)/100
On calculating we get Average atomic mass = 199.08 ≈ 199amu
Answer : (c)