Answer:
21.4 mL
Step-by-step explanation:
Firstly, one has to understand some "terms" here before proceeding.
60.0% solution of NaOH means 60g of NaOH salt/solute in 100 mL of water
35.0% solution of NaOH also means 35g of NaOH salt/solute in 100 mL of water.
To solve the problem in the question, we say, if 60 g dissolves in 100 mL, how many grams will be present in 30 mL
60 ⇒ 100
? ⇒ 30
? = 60 × 30/100
? = 18g
18 g of NaOH will be present in 30 mL of the solution making the % weight per volume to be 18/30
Thus, if we want to achieve 35% solution of NaOH from 18/30, the total amount of water that will be required will be ?
35 ⇒ 100
18 ⇒ ?
? = 18 × 100/35
? = 51.4 mL
Hence, the milliliters of water that must be added is 51.4 - 30 = 21.4 mL