Answer:
65.8mL of water and 184.2mL of the 95% EtOH stock solution must be added.
Step-by-step explanation:
To solve this question we need to find hoy many times the 95% EtOH must be diluted to obtain a 70% EtOH solution. That is:
95% / 70% = 1.357 times the solution must be diluted.
If we want to make 250mL of the diluted solution, the amount of 95% that must be added is:
250mL / 1.357 times =
184.2mL of the 95% solution must be added
And of water:
250mL - 184.2mL = 65.8mL of water