Question

Calculate the concentration of a solution of sodium
chloride, which was made by dissolving 1.16 g of solid
sodium chloride in water and making the solution up
to 250 cm. (Atomic mass of Na = 23 u, Cl = 35 u)​

Answer 1

Answer:

One molar solution of a compound is defined as the solution that contains 1 gram molecular weight of the compound dissolved in one liter of water.

Thus for the above question;

1M = Mol wt. of NaCl dissolved in 1000 ml of water

Hence, 1 M = 58.44 g NaCl in 1000 ml water

 

In 250 ml of the solution, the amount of NaCl dissolved to form 1 M solution, i.e. x, is calculated as:

 

1 M = 58.44 g = 1000 ml

1 M = x g = 250 ml

X = (58.44 x 250) / 1000

  = 14.61 g

Thus, 14.61 g of NaCl is dissolved in 250 ml to form a 1 M solution

 

The molarity of the solution (x M) when 1.16 g of NaCl is dissolved in 250 ml is calculated as;

 

Using the above relationship;

1 M = 14.61 g = 250 ml

x M = 1.16 g = 250 ml

 

Since the volumes in both the equations are same, we disregard it and use the remaining factors for determining the molarity .

 

x M = (1.16 g x 1 M) / 14.61 g

       = 0.08 M

 

Thus the molarity of 250 ml of NaCl solution is 0.08 M