FIRST ORDER CHEMICAL KINETICS: INVERSION OF SUCROSE ABSTRACT

By: Carla Mateo

The main purpose of the experiment is to measure the rate of inversion of sucrose and its dependence on temperature.  When discussing inversion, the origin of the usage of the term, in this context, comes from the way that the measurement is carried out.  The sugar syrup concentration is measured using a polarimeter.  The light, which is plane polarized, passes through a solution, a sample of pure sucrose, it undergoes a rotation.  It is optically rotated to the right.  During this process, the solution undergoes a transformation, converting it to a mixture of fructose, glucose and sucrose.  As this process takes place, the amount of rotation is diminished until it reaches a solution that is fully converted, and the rotation direction has been inverted, now from right to left.

For the procedure, we are going to place 15 to 20 grams of sucrose into a 100-ml volumetric flask, then add 50 ml of room temperature distilled water and shake to dissolve.  After this is done, we are going to fill the polarimeter tube with distilled water and calibrate each polarimeter for a zero reading correction.  Then we’ll pipet 25 ml of room temperature 3 N HCl into the sucrose solution, start the timer and add room temperature distilled water to the 100 ml mark and mix thoroughly.  To prepare the polarimeter we’ll rinse the tube sufficiently with the sucrose solution and fill with the solution, then start the measurements of the angle of rotation, αt, vs. time as soon as possible and repeat periodically. The main hazard of this experiment is that HCl is corrosive.