The teacher instructed three students ‘A’, ‘B’ and ‘C’ respectively to prepare a 50% (mass by volume) solution of sodium hydroxide (NaOH). ‘A’ dissolved 50g of NaOH in 100 mL of water, ‘B’ dissolved 50g of NaOH in 100g of water while ‘C’ dissolved 50g of NaOH in water to make 100 mL of solution. Which one of them has made the desired solution and why?

AcademicChemistryNCERTClass 9

According to the question,
50% mass by volume percent solution means 50 grams of a solute dissolved in 100 mL of solution. Therefore, student C made the desired solution.

Student A dissolved 50 g of NaOH in 100 ml of water, So the solution is diluted and it is not a desired solution.

Student B dissolved 50 g of NaOH in 150 g of solution so, it is not the desired solution.
Student C has made the desired solution by dissolving 50 g NaOH in water to make the volume of the solution 100 mL.
[ Extra information: %w/v = 100 × weight of solute
∴ %50 = 100 × weight of solute / 100 ml

weight of solute = 50 ×100 ml / 100
∴  weight of solute = 50 g

Here, 50g NaOH is required for 50% w/v 100ml solution of NaOH.]


raja
Updated on 10-Oct-2022 13:29:37

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