Question

Three students A, B, and C wanted to prepare a 60% (W/V) solution of sodium chloride. A dissolved 60 g of the salt in 100 mL of water, B dissolved 60 g of the salt in 100 g of water and C dissolved 60 g of the salt in water and made the volume of the solution to 100 mL. Which of them made the desired solution. Justify by calculating the strength of each.

Answer 1

Solute: A substance that is present in less quantity in solution.

Solvent: A substance that is present in more quantity in solution.

Student C will make the desired solution.

• Strength= mass of solute/volume of solution.
• To make 60% (W/V) solution of sodium chloride, 60 g of solute for every 100 mL of solution.
• Student C dissolved 60 g of the salt in water and made the volume of the solution to 100 mL.
• Strength= 60/100
• Strength= 60%(W/V)

So, student c is correct.

Incorrect:

Student A dissolved 60 g of the salt in 100 mL of water.

• Here, salt is solute and water is solvent.
• If the solvent is already 100 mL then an overall solution will be more than 100 mL.
• The volume of the solution is not known so the strength can not be calculated.
• Therefore incorrect.

Student B dissolved 60 g of the salt in 100 g of water.

• Here, salt is solute and water is solvent.
• The weight of solute and weight of the solvent is given.
• The volume of the solution is not known so the strength can not be calculated.
• Weight/weight ratio can be calculated rather than weight/volume ratio.