ExamHabit
Practise free

AIEEE 2009

JEE Main 2009 Chemistry question on Atomic Structure

Given that the abundances of isotopes 54Fe_{54}\text{Fe}, 56Fe_{56}\text{Fe} and 57Fe_{57}\text{Fe} are 5%, 90% and 5%, respectively, the atomic mass of Fe is
  1. A.
    55.85
  2. B.
    55.95
  3. C.
    55.75
  4. D.
    56.05
Show answer and solution

Correct option: B

Solution

Atomic mass = (5/100)×54 + (90/100)×56 + (5/100)×57
= 2.70 + 50.40 + 2.85
= 55.95

The weighted average of the isotopic masses using their percentage abundances directly gives 55.95 u.

[AIEEE 2009]

Practise Atomic Structure the way it is asked

A timed set of real JEE Main Atomic Structure questions, graded as the exam grades. No sign-up.

Start a Atomic Structure test

More: all JEE Main Atomic Structure questions · JEE Main 2009 · Chemistry chapter list