Question

7 10, 12 15 ppm) when 1. Detail how you intend to prepare the following calibration standards (1, 2, 3, 5, provided a 200 ppm stock dve solution. Th Reminder the smallest volume you can accurately pipette (using the provide glassware) is 1 ml. You may need to prepare a stock solution e final volume of the calibrations standards should be 25 ml

Answer 1

We have a 200 ppm stock dye solution. rightarrow we have to prepare solution of 1, 2, 3, 5, 7, 10, 12, 15 ppm. from the formula, v_1 s_1 = v_2 s_2 (it comes from the mole balance) where, v_1 = volume of the stock solution s_1 = conc. of the stock solution = 200 ppm v_2 = volume of the target solution = 25 ml (given) s_2 = conc. of the target solution. for s_2 = 15 ppm v_1 Times 200 = 25 Times 15 implies v_1 = 25 Times 15/200 = 15/8 but we do not have pipette that can measure less than 1 ml accurately so, clearly we have to make higher concentration solution & then by successive dilution we will reach to this value (15 ppm). let's make 120 ppm solution 25 ml thus, v_1 Times 200 120 Times 25 rightarrow v_1 = 15 ml thus, we need to mix 15 ml