Question

A student prepared a 1:1 buffer, for which [HAc] = [Ac-] = 0.05359 M. Using their 1:1 buffer and a 0.10038 M HCl solution, the student prepared Solution C in which 20mL of 1:1 buffer is mixed with 5mL of HCl. Given this information, how many moles of HCl were there in the student's Solution C before a reaction took place? Report your final answer, in moles, to 6 decimal places and only include the numerical value (no units).

Answer 1

By multiplying the volume of the HCl solution (5 mL or 0.005 L) by its concentration (0.10038 M), we found that there were 0.000502 moles of HCl in the student's Solution C before any reaction.

Step-by-step explanation:

The moles of HCl in the student's Solution C before a reaction took place can be calculated by multiplying the volume of HCl solution added to the buffer by its concentration. In this case, 5 mL (which is 0.005 L) of 0.10038 M HCl solution was used. Hence, the number of moles of HCl is:

# moles HCl = Volume (L) × Concentration (M) = 0.005 L × 0.10038 M = 0.000502 moles. To report this number to six decimal places, it becomes 0.000502 moles.

A buffer is a solution that resists changes in pH when an acid or a base is added to it. It's composed of a weak acid and its conjugate base (or a weak base and its conjugate acid) in equilibrium, helping to maintain the solution's pH within a relatively narrow range.