Answer:
To prepare 500ml of a approximately 0.20 mole of soduim hydroxide (NaOH) using solid sodium chloride, you will need to:
Obtain the necessary materials: 500ml of distilled water, 0.20 moles of solid sodium chloride (NaCl) and a container.
Slowly add the solid sodium chloride to the distilled water while stirring the solution.
Use a thermometer to monitor the temperature and stop adding the solid sodium chloride when the temperature reaches 90-100 °C.
The solution will become cloudy and will start to release heat. Allow it to cool down, and then measure the final volume of the solution.
The obtained solution will be a approximately 0.20M of sodium hydroxide.
Please note that this method is called "precipitation method" and it is not the only method to prepare sodium hydroxide solution, and also this method is not safe to handle and should only be done by trained person with proper lab equipment and safety measures.