Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: 3.1500 g of hydrated oxalic acid dissolved in water to make 250.0 mL solution will result in 0.1 M oxalic acid solution.
Reason R: Molar mass of hydrated oxalic acid is 126 g mol$$^{-1}$$.
In the light of the above statements, choose the correct answer from the options given below:

Assertion A: 3.1500 g of hydrated oxalic acid dissolved in water to make 250.0 mL solution will result in 0.1 M oxalic acid solution.

Reason R: Molar mass of hydrated oxalic acid is 126 g mol$$^{-1}$$.

Hydrated oxalic acid is $$H_2C_2O_4 \cdot 2H_2O$$.

Molar mass = $$2(1) + 2(12) + 4(16) + 2(18) = 2 + 24 + 64 + 36 = 126$$ g/mol.

Therefore, Reason R is TRUE.

$$\text{Moles of oxalic acid} = \frac{3.1500}{126} = 0.025 \text{ mol}$$

$$\text{Volume of solution} = 250.0 \text{ mL} = 0.250 \text{ L}$$

$$\text{Molarity} = \frac{\text{moles}}{\text{volume in litres}} = \frac{0.025}{0.250} = 0.1 \text{ M}$$

Therefore, Assertion A is TRUE.

The calculation in Assertion A directly uses the molar mass of 126 g/mol stated in Reason R. Without knowing the molar mass, we cannot compute the molarity. Hence, Reason R is the correct explanation for Assertion A.

The correct answer is Option (3): Both A and R are true and R is the correct explanation of A.