The density of solution prep. by dissolving 120g urea in 1kg h2o is 1.15g/mL. Molarity?

Question

A 2.05M

B 0.50M

C 1.78M

D 1.02M

Answer 1

As We know that

Density of solution  = Mass of solution / Volume of solution 

therefore , volume of solution  = Mass / density =   120+1000 g/ 1.15 g ml^-1 

= 1120 *100 / 115  = 973.91 ml = 974 * 10 ^-3 litres 

Now ,

n (no. of moles of solute) = 120 g / 60.05 g = 2 mol [since, molecular mass of urea is 60.05 g]

Now ,M(Molarity) = n (no. of moles of solute)/ Volume of solution in litres

 Molarity  = 2 / 974 * 10^-3

Molarity = 2000/974 = 2.05 M