Final answer:
A non-basic impurity in solid NaOH would cause the calculated molarity of HCl to appear higher during titration because there would be less reactive NaOH, requiring more HCl to reach the equivalence point.
Step-by-step explanation:
The effect of a non-basic impurity in solid NaOH on the calculated molarity of HCl during a titration would be that the molarity of HCl would appear higher than it actually is. Impurities in the NaOH would mean that there is less NaOH present to react with the HCl. As a result, more HCl would be required to reach the equivalence point, suggesting a higher concentration of HCl in the solution. This effect occurs because the stoichiometry of the reaction assumes that all of the NaOH is pure and can fully react with HCl to produce water and salt. Any non-reactive impurity would decrease the amount of NaOH available to neutralize the acid, thus altering the titration result.