Final answer:
When the endpoint in the titration of HCl with NaOH is overshot, the reported molar concentration of the HCl solution would be too low because the amount of NaOH added exceeds the HCl present.
Step-by-step explanation:
If the endpoint in a titration to standardize an HCl solution is 'overshot', this means that too much of the base, in this case, the sodium hydroxide (NaOH), has been added. This results in a lower concentration of HCl being calculated than the true concentration. In a titration, when the correct endpoint is reached, the amount of acid and base are chemically equivalent, which means the number of moles of HCl should equal the number of moles of NaOH used. If the endpoint is overshot, more NaOH has been added than there is HCl to react with, so the calculated concentration of HCl in the solution would be too low, as it is based on an excess volume of NaOH.