Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NEETChemistrySome Basic Concepts of Chemistry

Assertion (A): 12.5 g of an impure sample of magnesium carbonate ( MgCO ₃ ) requires 100 mL of 2.0 M HCl for complete reaction, so its percentage purity is 84 % . Reason (R): The balanced chemical equation for the reaction is MgCO ₃ + 2 HCl MgCl ₂ + H ₂ O + CO ₂ and the molar mass of MgCO ₃ is 84 g mol ⁻¹ . In the light of the above statements, choose the most appropriate answer from the options given below:

Options

  1. AAssertion (A) is false but Reason (R) is true.
  2. BBoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
  3. CBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
  4. DAssertion (A) is true but Reason (R) is false.

Correct answer

A. Assertion (A) is false but Reason (R) is true.

Step-by-step solution

Moles of HCl used = Molarity Volume (in L) = 2.0 0.100 = 0.2 mol From the balanced equation given in the Reason: MgCO ₃ + 2 HCl MgCl ₂ + H ₂ O + CO ₂ 2 mol of HCl reacts with 1 mol of MgCO ₃ . So, 0.2 mol of HCl will react with 0.1 mol of pure MgCO ₃ . Mass of pure MgCO ₃ required = Moles Molar mass = 0.1 84 = 8.4 g Percentage purity of the sample = ( Mass of pure substance Total mass of sample ) 100 = ( 8.4 12.5 ) 100 = 67.2 % The Assertion claims the percentage purity is 84 % , which is incorrect. Hence, Assertio

Practice Some Basic Concepts of Chemistry on Quantrex Academy →

More from Some Basic Concepts of Chemistry

Calculate the mass of potassium chlorate required to liberate 6.72 dm ^3 of oxygen at STP. [Molar mass of potassium chlorate = 122.5 g mol ⁻¹ ] 2026Find the mass of lime obtained by heating 500 g of 90 % pure lime stone. [Molar masses Ca =40 g/mol, O =16 g/mol & C =12 g/mol] 2026A coordination complex contains 2.6 % of Mg. Find the number of Mg atoms in 5.0 g of this sample. (gram atomic mass of Mg = 24 g ) 2026Calculate the number of moles and molecules of chlorine in 4.48 dm ^3 of chlorine at STP. 2026What is the gram atomic mass of an element whose mass of one atom is 3.9853 10⁻²³ g ? 2026Calculate the total mass and number of molecules present in 3 moles of benzene. 2026Which of the following gases has high vapour density at same temperature and pressure? 2026What is the number of moles of Cl atoms present in n moles of tear gas and in n moles of mustard gas respectively? 2026 Full Some Basic Concepts of Chemistry list All NEET PYQs