To prepare one liter of one molar solution of sodium hydroxide we need one mole of sodium hydroxide. you will need to dissolve 40 g of sodium hydroxide in one liter of water to get one liter of 1 molar solution.

definition

Molarity

Molarity(M) of a solution is defined as the number of moles of solute dissolved per litre of solution. Molarity$=$$VolumeofsolutioninlitresNo.ofmolesofsolute $

formula

Molarity equation

If a solution having molarity $M_{1}$ and volume $V_{1}$is diluted to volume $V_{2}$ so that the new molarity is $M_{2}$ then as the total number of moles will remain constant, we have $M_{1}V_{1}=M_{2}V_{2}$