To prepare 250 mL standard solution of M/20 NaCl, amount of NaCl required is :

0.73 g

The correct answer is option 2. 0.73g

To prepare a standard solution of M/20 NaCl, we need to calculate the mass of NaCl required.

Molarity (\(M\)) is defined as moles of solute per liter of solution. For a M/20 solution, it means that there are \(1/20\) moles of NaCl per liter of solution.

Given that we want to prepare a 250 mL (\(0.25\) L) solution, the number of moles of NaCl required can be calculated using the formula:

\[ \text{Moles of solute} = \text{Molarity} \times \text{Volume of solution (in liters)} \]

Substituting the given values:

\[ \text{Moles of NaCl} = \frac{1}{20} \times 0.25 \]

\[ \text{Moles of NaCl} = \frac{0.25}{20} = 0.0125 \, \text{moles} \]

Now, to calculate the mass of NaCl required, we use its molar mass, which is approximately \(58.44 \, \text{g/mol}\).

\[ \text{Mass of NaCl} = \text{Moles of NaCl} \times \text{Molar mass of NaCl} \]

\[ \text{Mass of NaCl} = 0.0125 \, \text{moles} \times 58.44 \, \text{g/mol} \]

\[ \text{Mass of NaCl} = 0.732 \, \text{g} \]

Therefore, the correct answer is option \((2)\) \(0.73 \, \text{g}\).