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NEETChemistrySome Basic Concepts of Chemistry

A metal oxide has the empirical formula M ₂ O ₃ . If the oxide contains 30 % oxygen by mass, the atomic mass of the unknown metal M is : (Given atomic mass of O = 16 u )

Options

  1. A112 u
  2. B160 u
  3. C56 u
  4. D80 u

Correct answer

C. 56 u

Step-by-step solution

Let the atomic mass of the metal M be x . The empirical formula of the metal oxide is M ₂ O ₃ . Mass of oxygen in one mole of the empirical formula = 3 16 = 48 u . Total molar mass of the empirical formula = 2x + 48 u . It is given that the mass percentage of oxygen is 30 % . 48 2x + 48 100 = 30 48 2x + 48 = 0.30 48 = 0.60x + 14.4 0.60x = 33.6 x = 33.6 0.60 = 56 u Thus, the atomic mass of the metal M is 56 u . Answer: 56 u

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