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Potassium chlorate ( KClO ₃ ) on heating decomposes to yield potassium chloride ( KCl ) and oxygen gas ( O ₂ ). What is the mass (in g) of KClO ₃ required to produce 9.6 g of O ₂ gas upon complete decomposition? (Given Molar mass in g mol ⁻¹ : K =39 , Cl =35.5 , O =16 )

Options

  1. A36.75
  2. B49.0
  3. C24.5
  4. D55.1

Correct answer

C. 24.5

Step-by-step solution

The balanced chemical equation for the thermal decomposition of potassium chlorate is: 2 KClO ₃( s ) 2 KCl ( s ) + 3 O ₂( g ) Molar mass of O ₂ = 2 16 = 32 g mol ⁻¹ Moles of O ₂ produced = 9.6 32 = 0.3 mol From the stoichiometry of the balanced equation, 3 moles of O ₂ are produced from 2 moles of KClO ₃ . Moles of KClO ₃ required = 2 3 0.3 = 0.2 mol Molar mass of KClO ₃ = 39 + 35.5 + (3 16) = 122.5 g mol ⁻¹ Mass of KClO ₃ required = 0.2 122.5 = 24.5 g Answer: 24.5

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