If a small amount of the unknown solute fails to dissolve in the lauric acid, will the molar mass that you calculate for unknown solute be too high or too low?

If the solute fails to dissolve in the lauric acid, the molar mass that can be calculated based on the concentration of the solute dissolved in the lauric acid would be too low. This is because there are unaccounted masses that cannot be included in the calculation. This is a case of underestimation of the molar mass.

To avoid that this happens, ensure that all of the solute dissolves well in solvent by mechanical means (stirring, shaking, etc) or introducing heat.