Verified Solution • 2025–26 Session moderate

QJEEM23Ch79a3: JEE Main 2023 Chemistry - Class 11 JEEM23Ch79a3 Solution: Given below are two statements: one is labelled as Assertion…

Given below are two statements: one is labelled as Assertion A\mathbf{A} and the other is labelled as Reason R\mathbf{R}

Assertion A : 3.1500 g3.1500 \mathrm{~g} of hydrated oxalic acid dissolved in water to make 250.0 mL250.0 \mathrm{~mL} solution will result in 0.1 M0.1 \mathrm{~M} oxalic acid solution.

Reason R\mathbf{R} : Molar mass of hydrated oxalic acid is 126 g mol−1126 \mathrm{~g} \mathrm{~mol}^{-1}

In the light of the above statements, choose the correct answer from the options given below.

Multiple Choice Options

  • A Both A and R are true but R is NOT the correct explanation of A
  • B A is true but R is false
  • C Both A and R are true and R is the correct explanation of A
  • D A is false but R is true

Step-by-Step Verified Solution

Firstly, let's calculate the molarity of the oxalic acid solution given in the Assertion (A).

The molarity (M) is defined as the number of moles of solute per liter of solution. The number of moles of solute is given by the mass of the solute divided by its molar mass.

So, the number of moles of hydrated oxalic acid is 3.1500 g126 g/mol=0.025 mol\frac{3.1500 \, \text{g}}{126 \, \text{g/mol}} = 0.025 \, \text{mol}

And the volume of the solution is 250.0 mL, or 0.250 L.

Therefore, the molarity of the solution is 0.025 mol0.250 L=0.1 M\frac{0.025 \, \text{mol}}{0.250 \, \text{L}} = 0.1 \, \text{M}

This matches the molarity given in the Assertion (A), so the Assertion is true.

The Reason (R) gives the molar mass of hydrated oxalic acid as 126 g/mol, which was used in the calculation above. Therefore, the Reason is also true.

Moreover, the Reason (R) is the correct explanation of Assertion (A), as it provides the necessary information (the molar mass of hydrated oxalic acid) to calculate the molarity of the solution.

So, the correct option is C: Both A and R are true and R is the correct explanation of A.

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