Complete the calculations below based on the following student data. A student following the procedure similar to that in this lab prepared four solutions by adding 12.25, 23.00, 25.50, and 34.50 mL of 8.25 x 10-2 M NaOH solution to 50.00 mL of a 0.152 M solution of weak acid. The solutions were labeled 1, 2, 3, and 4 respectively. Each of the solutions was diluted to a total volume of 250 mL with DI water. The pH readings of these solutions were: (1) 6.64 (2) 6.98 (3) 7.04 (4) 7.23. PRE-LAB DATA SHEET
1 2 3 4
Initial number of moles
HAn(aq)
OH-(aq)
Number of moles at equilibrium
HAn(aq)
An-(aq)
Equilibrium concentrations, mol/L
HAn(aq)
An-(aq)
H3O-(aq)
Ka
Average Ka
Which of the weak acids in Table 1 do you think your unknown acid is?