How much concentrated HCl (12 M) is needed to make 500 ml of 0.5 M HCl?   Given a standard solution of 1 M sodium hydroxide, describe the preparation of 250 ml of 0.25 M NaOH.   How many cubic centimeters of glacial acetic acid (17 M) are needed to make 2.5 liters of vinegar (1 M).