[rorl]

5) What is the mass of KCl in 250mL of a 3% (w / v) solution of this salt? Answer: 7.5 g

6) Which mass of Na2CO3 of purity equal to 80% should be dissolved in water to prepare 500 ml of a 2% (w / v) solution? Answer: 12.5 g



5) What means 3% in this case ? I know that x %(solute mass /solution volume) represent that in 100 mL of solution, there is x% of solute mass. But I don't understant this question.

6) What is a purity in this case ? I've no idea.


Thanks for help me. Can you indicate a book for me ? I'm a electrical engineer student.

[Borek]

3% w/v means 3 g per 100 mL, that's exactly what the definition states, no idea where you have problem.

80% purity means the compound is 80% of the sample, the other 20% being impurities.