Question

A solution of NaCl has a milliosmolarity of 200. How many grams of NaCl were added to a 1 liter container of pure water to produce this solution?

Answer 1

Given that

osmolarity of Nacl solution is 200milliosmolarity

when the Nacl is amde into a solution using water , the ions generated are 1Na+ and 1cl- ion

So, 1 mol of Nacl solution will provide 1mol of Na+ ion and 1 mole of cl- on dissociation

Molarity of the solution is obtained by dividing the Osmolarity of the solution with number of ion it formed in the solution .

Her,Nacl dissociate to form 2 particle(Na+ and cl-)

So the molarity of the Nacl solution = osmolarity of the Nacl / number of particles = 200milliosmol/2 = 100millimolar

Molarity of the solution is defiend as the number of moles of solute present in 1LITER of solution.

Here the solution is made up of 1Liter of water, so the molarity of the solution is equal to the Number of moles of Nacl

Number of moles Nacl = 100millimol

We know that number of moles = Amount of Nacl in grams /Molecular mass of the compund in grams

100millimol = Amount of Nacl in grams /58.5

Amount of Nacl in grams = 100 *10-3 mole *58.5 = 5.85 grams.

SO, 5.85grams of Nacl is to be needed for producing a Nacl Solution with 200milliosmolar