Answer:
a. 150mL of the stock solution was added
b. 50mL of water was added
Step-by-step explanation:
The solution was diluted from 16.0M to 12.0M, that is:
16.0M / 12.0M = 1.333 times was diluted.
As the volume of the diluted solution is 200mL, the amount of the 16.0M stock solution is:
200mL / 1.333 =
a. 150mL of the stock solution was added
As the volume of the solution is 200mL and 150mL were added of the stock solution, the volume of water is:
200mL - 150mL =
b. 50mL of water was added