chem lab report and calculation

CHM 117 Experiment 3 Spring 2018

Stoichiometry of a Chemical Reaction Benchwork Instructions

• At your workstation you will find a 50-mL buret and a vial containing oxalic acid (H2C2O4).

• Before doing anything else, rinse the buret with deionized water a few times. To do this, close the stopcock, add about 10 mL of water from a wash water, using both hands place the buret in horizontal position and roll it so that the water inside covers the inside surface entirely. Let the water out through the buret tip to wash it also.

• Obtain about 50 mL of NaOH solution from the container in hood. Make sure to record the concen- tration of the solution. Fill the buret up. You do not need to fill up to the zero mark but get close to it. Let some solution run through the tip to fill it as well.

• Take the vial containing oxalic acid (H2C2O4) to the analytical balance. Weigh the vial, transfer about 0.2 g. of oxalic acid into a 250-mL Erlenmeyer flask, weigh the vial again and determine the exact mass of acid by difference. Record the exact value. Add about 100 mL of deionized water and 6-7 drops of phenolphthalein indicator to the 250-mL Erlenmeyer flask. Make sure the the solid dissolves completely.

• Titrate the dissolved acid with the NaOH solution in your workstation until the color of the solution changes from clear to a permanent pale pink. Record the exact volume of NaOH used.

• Repeat the procedure for one more sample of H2C2O4.

CHM 117 1 Spring 2018