If you had one gallon of concentrated hydrochloric acid (12 N) and added water to make dilute hydrochloric acid (6 N), how much dilute hydrochloric acid would you have?

Answer 1

You would have two gallons of solution.
vol x N = vol x N
1 gallon x 12N = gallons x 6N
vol =12/6 = 2 gallons.