the density of a solution prepared by dissolving 120g of urea in 1000g of water is 1.15g/ml .The molarity of soltuion is:

1.78M

1.02 M

2.05 M

0.5 M

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

Ans.

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