Question

the density of a solution prepared by dissolving 120g of urea in 1000g of water is 1.15g/ml .find the molarity & molality of this solution

Answer 1

Molarity = Number of moles of solute/Volume of solution in Litres

Moles of urea = Given mass/Molecular mass = 12060 = 2 mol

Volume of solution = Mass of solution/Density of solution= (120+1000) g/1.15 g.mL−1= 974 ml or 0.974 L

Hence, Molarity = 2 mol/0.974 L = 2.05 mol L−1 


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Answer 2

Answer:

Explanation:

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

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