POST LAB 2

Post Lab Report Name: Shejay G. Mandaing Lab-partner: Janel Mulleda Experiment 2. Recrystallization and Melting Point Determination of Benzoic Acid 1. How does the use if fluted filter paper hasten filtration? Why is it advisable to place a small piece of wire between the funner and the mouth of the flask during hot filtration? Fluting increases the speed of the filtering process through the combination of larger filtering area and facilitated flow.T he fluting allows the filtrate to pass through the paper and out of the filter body faster because each flute acts like a relief notch. Meanwhile, the filter body will allow the use of a filter paper of much larger area if it is fluted. A small piece of wire or paper is inserted between funnel and Erlenmeyer to prevent formation of a seal and subsequent pressure build-up. 2. Enumerate two techniques that can help prevent premature recrystallization. Explain each one. What is the consequence of premature recrystallization? Having the set up heated before filtration and Keeping the solution very hot so the solute stays dissolved will prevent crystals from forming on the paper and in the funnel. As the filtrate begins to accumulate, heating the receptacle beaker will also help to prevent any crystallization in the funnel or on the filter paper because of the resulting vapors . Also, If crystals have formed, pouring a small amount of boiling solvent through the funnel will dissolve these. If premature recrystallization occurs, then there eill be an error in the % recovery of the sample since some sample may have laready been lost in the premature recrystallization. 3. What solvent would you choose? Support your choice by means of a schematic diagram. Dissolve 0.2 g A and 8.0 g B in 100 mL acetone and boil for 1-2 minutes. (If some solids remain undissolved, add bopiling solvent in small portions to dissolve. ) Add a pinch of charcoal and gently heat to boiling Filter solution through fluted filter paper into another Erlenmeyer flask containing 3 mL of hot acetone Allow filtrate to cool slowly without diturbance Collect recrystallized sample by filtration Wash crystals with small amount of cold acetone Spread filter paper on watch glass and air dry

Report weight and % recovery References: Organic laboratory techniques 3. Retrieved 22 April 2013 from http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf Recrystallization. Retrieved 22 APri 2013 from http://chem.chem.rochester.edu/ ~chem207/Recrystallization.pdf Yauder, C. (2013). Recrystallization. Retrieved 22 APri 2013 from http://www.wiredchemist.com/chemistry/instructional/laboratory-tutorials/recrystallization