26)When performing a titration, a student adds three drops of phenolphthalein to a flask containing 40.1 mL of HCl. Using a buret, the student slowly adds 2 M NaOH to the flask until one drop causes the
indicator to turn light pink. The student determines that a total volume of 24.2 mL of NaOH was used
in this titration. Calculate the molarity of the HCl used in the titration. (10)

The scheme below is from a series of reactions that are part of a synthesis of vitamin a. answer the following questions with reference to this scheme. (i) what is "reagent a"? (ii) draw a step-by-step mechanism which explains the formation of compound c from compound b (iii) which reagents would you use to form compound e from compounds c and d (reagents b and c)? for each reagent suggested above in (ii) explain the role of the reagent in the reaction to (iv) form compound e. you may wish to do this by drawing a mechanism. 1. addition of reagent a но reagent a 2. н,о" thо oh нон-с compound a. compound b. compound c .ch-оh 1. reagent b "сно 2. reagent c сh oh compound e. compound d.