Question

A quantity of NaCl was dissolved in 100.0 cm^3 of solution to obtain 0.5 M Back solution. Determine the mass NaCl used. [Na=23, Cl=35.5]​

Answer 1

Answer:

The concentration indicated in the label, should be assumed as given in wt%, i.e. (g HCl / g solution)·100%. Commercial conc. HCl is typically 37 wt%. The density of 37.0 wt% HCl (aq.) solution is 1.184 g/cm3 (20 ºC) (*) ― likely available from the label. The molarity is: 0.37(g HCl / g aq. sol.)·1.184(g aq. sol. / cm3)·(1000 cm3/dm3)/(36.46 g HCl/mol HCl) = 12.02 M (approximate). The intended dilute solution (0.025 M) can be then volumetrically prepared, at approx. 20ºC, while considering the appropriate (volumetric) dilution factor. For quantitative analytical purposes the prepared solution should be standardized to accurately determine its molarity (approx. 0.025 M).