Question

2.5 litres of NaCl solution contain 5 moles of the solute. What is the molarity?
(a) 5 molar
(b) 2 molar
(c) 2.5 molar
(d) 12.5 molar

Answer 1

molarity is ratio of number of solute particles dissolved per litre of solution

Here 5 moles of solute are dissolved in 2.5 litres of NaCl so the molarity is 2 molar

Answer 2

Answer:

The correct answer is option (b) 2 molar.

Concept:

Molarity:  The number of moles of solute dissolved per litre of the solution at a particular temperature is called the molarity of the solution at that temperature.

Molarity = (Number of moles of solute)/(Volume of the solution in litres)

M = n/V

Molarity actually represents the concentration of a solution in mol L⁻¹.

Since the molarity involves volume which is dependent on temperature, the molarity of a solution changes with temperature.

Given:

Volume of the solution, V = 2.5 litres

Number of moles of solute, n = 5

Find:

The molarity of the solution.

Solution:

Molarity = n/V

M = 5/2.5

M = 2 moles/litre

Hence, the molarity of the solution is 2 moles/litre or 2 molar and the solution is called bimolar solution.

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