Commercially available concentrated hydrochloric acid contains 38% hcl by mass and has density 1.19 gcm-3 calculate molarity of hcl
Answers
Unless stated otherwise, the concentration indicated in the label, should be assumed as given in wt%. If considered valid for 20º C, the (approx.) density available from the label (1.19) actually corresponds to a 38 wt% solution. For 37 wt% ― the average concentration (rounded to nearest whole unit) of the concentration range provided in the label (36.5―38 wt%) ― it is a little bit more consistent to take 1.184 g·cm-3 for the density (20 ºC); rather than the label figure (cf. e.g. Perry's Chemical Engineers' Handbook). That also avoids temperature ambiguity, since the temperature is not explicitly stated for the density available from the label. The molecular mass of HCl is 36.46 g·mol−1. From previous data, the molarity of the conc. sol. is readily calculated. The intended dilute solution can be then volumetrically prepared, at approx. 20ºC, while considering the appropriate (volumetric) dilution factor. Also to be noticed is that the prepared dilute HCl aq. sol. is not a primary standard.