Answer:
The solution in the test tube would turn pink earlier with the more concentrated NaOH solution.
This is because the concentration of the NaOH solution is directly proportional to the number of moles of NaOH per unit volume of the solution.
So, with a more concentrated NaOH solution (1.0 M compared to 0.5 M), each mL of NaOH solution contains twice as many moles of NaOH.
Therefore, it would take half as much volume (i.e., 12.4 mL instead of 24.8 mL) of the 1.0 M NaOH solution to react with the same number of moles of the unknown acid as the 0.5 M NaOH solution.