48.70 mL of an HCl stock solution was transferred into a 500 mL volumetric flask and filled to the mark. 47.67 mL of the diluted solution was titrated with 0.179 M NaOH and found to have the concentration of 0.885 M. What is the concentration of the stock solution?

1 answer

The concn of the titrated solution is 0.885M. It came from the 500 mL flask; therefore, it must be 0.885M also. How many moles HCl are in the 500 mL flask? That will be 0.885 x 0.500L = 0.4425 moles.
All of those moles came from the 48.70 mL stock solution; thus, the M of the stock soln is 0.4425 moles/L = about 9M but that's just an estimate.