A 90% KCN solution is diluted with water to make a solution of 60% acid. When 3 gallons of water is added to dilute it again, the solution becomes 40% acid.
a. how much water was added to the solution on the first instance?
b. what was the original volume of the 90% acid solution?
K = the amount of KCN
w = the amount of water
a = amount of water added
K = 2 / 5
w = 18 / 5
a = 2
You should be able to answer a and b now.
By the way, KCN is the salt of a strong base KOH and a weak acid HCN therefore is it a base not an acid.
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.