To determine how many moles of HCl were in the student's Solution C before a reaction took place, we need to know how many liters of the HCl solution were used to prepare Solution C.
Assuming that the student used a specific volume V (in litters) of the 0.09926 M HCl solution, the moles of HCl can be calculated using the formula:
\[ \text{moles of HCl} = \text{concentration of HCl} \times \text{volume of HCl solution} \] \[ = 0.09926 , \text{M} \times V , \text{L} \]
To get the exact value, we need to know the volume in liters. If you provide the volume V used in part 3 for preparing Solution C, I can calculate the exact number of moles of HCl for you.
If no specific volume is mentioned, please clarify or provide additional information.