Answer Happy

Procedure: Part A - Measuring Chlorine Levels 1) Place four test tubes in a test tube rack and label them 1 - 4. 2) Place the test tube rack on a white sheet of paper. 3) Obtain about 2-3 mL of methyl orange indicator solution. 4) Using a labeled microtip plastic pipette, place 10 drops of methyl orange in test tube #1. 5) Obtain 2-3 mL of 0.5 M HCl solution. 6) Add 5 drops of 0.5 M HCl solution to test tube #1. Mix the solution by swirling the test tube. 7) Obtain about 25 mL of simulated pool water in a labeled beaker. 8) Carefully add the simulated pool water drop by drop to test tube #1. Mix the solution between drops by swirling the test tube. Record the number of drops required to change the solution from a red color to a pale yellow. 9) Repeat steps 3 - 8 for three more samples in test tube #2, #3 and #4. 10) Dispose the final solutions into the sodium bicarbonate waste beaker.
Procedure: Part B Effect of Urea on Chlorine Level. 11) Label four beakers and label them 5, 10, 15 and 20. 12) Drops of 0.1 M urea solution have been added to samples of simulated pool water (5, 10 or 15 drops). Obtain about 5 mL of each and place them in the labeled beakers. 13) Test the chlorine level in each sample using steps 3-8 in part A. 14) Obtain an unknown sample from your teaching assistant. Record the code for your unknown. Test the chlorine level in this sample. Repeat if needed. 15) Dispose the final solutions into the sodium bicarbonate waste beaker.
Data Tables and Results - Part A 1ML-35 DROPS POOL WATER #1 #2 Drops of methyl orange solution Drops of 0.5 M HCI Drops of pool water Chlorine concentration (M) Chlorine concentration (ppm) 10 5 580 10 5 445 10 5 437 #3 10 5 420 #4 average U/A U/A 470.5
Data Tables and Results Part B 1ML-35 DROPS POOL WATER + 10 drops urea Drops of methyl orange solution 10 Drops of 0.5 M HCI Drops of pool water Chlorine concentration (M) Chlorine concentration (ppm) 5 150 + 50 drops urea 10 5 55 10 5 47 + 15 drops urea 10 LO 5 35 +20 drops urea unknown F 10 5 50
Post Lab Calculations Molarity of the methyl orange solution is 0.0015 M. 1) For each titration, calculate the concentration of chlorine in the simulated pool water in units of molarity and parts per million for chlorine. Enter values in the data tables. 2) Average the free residual chlorine concentration values for each pool water sample. Enter these values in the data tables. 3) Graph the chlorine concentration in parts per million versus the drops of urea solution added. The free residual chlorine concentration should be plotted on the Y-axis and the drops of urea solution should be plotted on the X-axis. 4) Use the graph to determine how many drops of urea were added to the unknown solution.