You have a stock solution of 15.0 M NH3 . How many milliliters of this solution should you dilute to make 1200ml of 0.280 M NH3 ?

Answer 1

find the moles of NH3 you need:
moles=.280*volume=.280*1.2=xxxx liters
Now, find the volume of stock solution needed to deliver those moles..

volume=xxxx/15
so take 1000*xxxx/15 ml of stock solution, and the remainder water.
stir, properly label, and you are done.