posted by rahim .
We want to make 40. mL of 0.50 M HCl by diluting the stock 2.0 M HCl solution with water. What volume of 2.0 M HCl solution is needed?
lets see. You want to dilute it 4 times, so you need three parts water, one part original. Isn't that 10ml original, and 30ml of water?