A student obtains 25.00 mL of an HCl solution of unknown concentration. Upon titration, 21.35 mL of 0.1200 M NaOH are required for neutralization. Determine the concentration of the HCl solution. the capital M is molar mass right? but i thught that was constant so how can it be 0.1200 M NaOH? or do they mean m for mols so the first thing you need to do is write the equation NaOH + HCL = NaCl + H2O using the mol ration, the number of mols will be the same for every thing elce soo... now what?