Question

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?
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Answer 1

Answer:

Student A and B make solution about 150 ml so,

student c make desire solution bcoz he add water to make 100 ml solution.

and from calculation,

%w/v = 100 × weight of sub (solute)

                 volume of solution

∴ %50 = 100 × weight of sub

                    100 ml

   weight of sub = 50 ×100 ml

                               100

∴  weight of sub = 50 g

here the 50g NaOH requred for 50% w/v 100ml solution of NaOH

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Answer 2

Answer:

Student C

Explanation:

Student C prepared it correctly as 50% mass by volume means 50g of solute for every 100 ml of solution (not in 100 ml of solvent)

mass by volume % = mass of solute/vol of solution *100