I need a 64% solution of ammonium chloride. I have 99% ammonium chloride powder. How many grams of the NH4CL do i need to add to 500 ml of water to get the 64% solution?
I will assume you mean mass/volume percent. 64% w/v means 64g NH4Cl in 100 mL solution. We will assume the volume will not change (a false assumption).
64 g/100 mL means 64 x (500/100) = ? g/500 or about 320 g NH4Cl if it were 100%. It is only 99%; therefore you will need about 320/0.99 = ?