1. When phenolphthalein reacts with a strong base solution, the concentration of phenolphthalein, C (in moles

per liter) decreases over time, as shown in the table below1.

t (seconds) 0.0 10.5 22.3 35.7 51.1 69.3

C (moles per liter) 0.0050 0.0045 0.0040 0.0035 0.0030 0.0025

(a) Find the average rate at which the concentration of phenolphthalein is decreasing during the rst

t = 10:5 seconds.

(b) Is the rate of the chemical reaction speeding up or slowing down as time goes on? Explain your answer.