Asked in FBISE Chemistry 2022 SLO — Paper 3 2022

Mass spectrum of Magnesium shows that it contains three isotopes. Mg-24 (78.70%), Mg-25 (10.13%) & Mg-26(11.17%). The average atomic mass of Mg is

Correct answer: A. 24.32 amu

  • A. 24.32 amu
  • B. 25.32 amu
  • C. 26.32 amu
  • D. 27.32 amu

Explanation

To calculate the average atomic mass, we use the formula:Average atomic mass=(Abundance1×Atomic mass1)+(Abundance2×Atomic mass2)+(Abundance3×Atomic mass3)Substituting the values:Average atomic mass=(0.7899×23.98504 )+(0.1000×24.98584 )+(0.1101×25.98259 )Average atomic mass=18.99254 +2.49858 +2.86561 Average atomic mass=24.35673 So, the average atomic mass of magnesium is approximately 24.35673

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