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Calculate the weight of the unknown sample needed to produce a 40mL [Cl-] solution of about 0.02M. Assume that the weight percent of NaCl in the unknown sample is 50%.

My answer:

(0.02 mol/L) x (0.04L) x (22.990g NaCl/ mol)

= 0.018392 g x 2 <=== because the sample contains only 50% NaCl

= 0.036784 g

is that the right way? Thanks again.

and does anyone know why it has to be 0.02M? is it because we are going to use 0.02M of AgNO3 to precipitate out the Cl-