how do you make a 10ml solution with a .40m concentration

Question

I know it has to do with molars and making a solution that we can measure how much light goes through it because we are doing concentration.

Answer 1

Molarity is a measure of moles per liter.  So you need to set up the equation as [m] = moles/liters.  So if you need a 10 ml solution with a .4m concentration you need to fill the equation in.  You know you need [m] to equal .4 and you know you need .010 liters.  So solve for moles. .4 = x/.01  == .4*.01=.004.  So you need .004 moles of your molecule.  A mole is 6.022 x 10²³  (602200000000000000000000).  So next what you need to do is find the molar mass of you molecule which is found of the periodic table.  For example H₂O₂ (hydrogen peroxide) would have a molar mass of O=16 H=1 so ((16*2)+(1*2))= 34 grams a mole.  Once you found how many grams a mole your molecule is then you times it times your wanted moles, in your case .004, and you have how many grams you need to put into your solution.