UPSEE Solved Model Paper 7

Given :
Percentage of

54

‌

Fe = 5
Percentage of

56

‌

Fe = 90
Percentage of

57

‌

Fe = 5
We have to find the relative atomic mass of Fe.
Weight of any element is given by :
Weight of element = Σ (Percentage abundance of isotope × Atomic mass of isotope)
Thus,
Weight of

54

‌

Fe = 0.05 × 54
= 2.7
Weight of

56

‌

Fe = 0.9 × 56
= 50.4
Weight of

57

‌

Fe = 0.05 × 57
= 2.85
Now,
Relative atomic mass of Fe = 2.7 + 50.4 + 2.85
= 55.95
Hence, option 'B' is correct