Question

Pls help me by providing practice Questions for concentration terms

Answer 1

If 2 moles of salt is dissolved to form 1 liter of solution, calculate the molarity of the solution.

a. 1 M solution

b. 1.5 M solution

c. 2 M solution

d. 2.5 M solution

The formula for calculating molarity when the moles of the solute and liters of the solution are given is = moles of solute/ liters of solution.

Moles of Solute = 2 moles of sugar

Solution liters = 1 liters

The molarity of the solution = 2 moles of solvent/1 liters of solution = 2 M solution

Two solutions of a substance (non electrolyte) are mixed in the following manner. 480 mL of 1.5 M first solution + 520 mL of 1.2 M second solution. What is the molarity of the final mixture?

(AIEEE 2005 - equivalent to IIT JEE MAIN)

1) 1.20 M

2) 1.344 M

3) 1.50 M

4) 2.70 M

Logic & Solution:

Molarity of a mixture, M_mix can be calculated by:

M_mix = (M₁V₁ + M₂V₂) / (V₁ + V₂) = (1.5 x 480) + (1.2 x 520)/(480 + 520) = 720+624/1000 = 1.344 M

Conclusion:

The correct option is '2'.

The density of a solution prepared by dissolving 120 g of urea (mol.mass = 60 u) in 1000 g of water is 1.15 g/mL. The molarity of this solution is:

(AIEEE 2012)

1) 1.02 M

2) 2.05 M

3) 0.50 M

4) 1.78 M

Solution:

Molarity of a solution (M) = n/V

Where:

n = number of moles of urea = 120/60 = 2 mol

V = volume of the solution = mass of solution / density of solution = (120 + 1000) g / 1.15 g mL^-1 = 974 mL = 0.974 L

Therefore:

M = 2 mol / 0.974 L = 2.05 mol L^-1

Note: Volume of solution should be expressed in litres.

Conclusion:

The correct option is '2'.