A Chemist needs to create a solution consisting of 90% hydrochloric acid(the other 10% is water.) How much pure acid(100% acid solution) should be mixed with 15ml of a solution with 40% acid in order to get a solution with 90% acid?
15ml of 40% hHcl is 6ml Hcl. Then (6+x)/(15+x)=.9
You need 75ml pure acid.
Hope that helps,