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NEETChemistrySome Basic Concepts of Chemistry

An impure sample of Mg(OH) ₂ weighing 1.16 g is completely neutralized by 40 mL of a 0.5 M HCl solution. What is the percentage purity of the Mg(OH) ₂ sample? (Given molar mass of Mg(OH) ₂ = 58 g mol ⁻¹ )

Options

  1. A100 %
  2. B25 %
  3. C50 %
  4. D75 %

Correct answer

C. 50 %

Step-by-step solution

The balanced chemical equation for the neutralization reaction is: Mg(OH) ₂( s ) + 2 HCl ( aq ) MgCl ₂( aq ) + 2 H ₂ O ( l ) Number of moles of HCl used = Molarity Volume in L = 0.5 M 0.040 L = 0.02 mol From the balanced equation, 2 moles of HCl neutralize 1 mole of Mg(OH) ₂ . Therefore, moles of pure Mg(OH) ₂ present = 0.02 2 = 0.01 mol . Mass of pure Mg(OH) ₂ = 0.01 mol 58 g mol ⁻¹ = 0.58 g . The percentage purity of the sample is given by: Percentage purity = Mass of pure substance Total mass of sample 100 Perce

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