In this experiment, your goal is to determine the amount of lead present in a water sample and, if lead is present, to determine whether the level of contamination is potentially dangerous. Preliminary preparation of the sample has resulted in a solid of unknown composition. This solid contains lead (Pb 2+ ) in the form of a water soluble salt and gravimetric analysis will be used to determine the amount of lead present. Step 1. Preparation of precipitating agents : Dissolve a predetermine amount of sodium sulfate in distilled water to produce 100mL with a concentration of 0.175M. Transfer the solution in the burette. Step 2. Obtain 3 10-mL sample of wastewater which contains lead in an erlenmeyer flask. Step 3. Dilute the 10 ml sample with water to 100mL. Step 4. Add an excess amount of sodium sulfate to achieved complete precipitation. Step 5. Filter the solution using a pre-weighed filter paper. Step 6. Collect the precipitates in filter paper and dry in an oven at 105 o C for 3 hrs or until completely dried. Step 7. Transfer the filter paper containing dried precipitates in a dessicator for 30 minutes to absorb the moisture during cooling. Step 8. Weigh the filter paper containing the dried precipitates using analytical balance. Step 9. Compute for the weight of the precipitates by difference. Step 10. Compute for the % lead in wastewater. Below are the data gathered during the experiment : Trial 1 Trial 2 Trial 3 Volume of sample 10mL 10mL 10mL Volume of added distilled water 90mL 90mL 90mL Volume of sodium sulfate 9mL 9mL 9mL Weight of filter paper 1.06 g 1.08 g 1.07 g Weight of filter paper + evaporating dish + precipitate after drying 35.6525 35.6565 35.2351 Weight of evaporating dish 34.4306 34.4325 33.9914
In this experiment, your goal is to determine the amount of lead present in a water sample and, if lead is present, to determine whether the level of contamination is potentially dangerous. Preliminary preparation of the sample has resulted in a solid of unknown composition. This solid contains lead (Pb 2+ ) in the form of a water soluble salt and gravimetric analysis will be used to determine the amount of lead present.
Step 1. Preparation of precipitating agents : Dissolve a predetermine amount of sodium sulfate in distilled water to produce 100mL with a concentration of 0.175M. Transfer the solution in the burette.
Step 2. Obtain 3 10-mL sample of wastewater which contains lead in an erlenmeyer flask.
Step 3. Dilute the 10 ml sample with water to 100mL.
Step 4. Add an excess amount of sodium sulfate to achieved complete precipitation.
Step 5. Filter the solution using a pre-weighed filter paper.
Step 6. Collect the precipitates in filter paper and dry in an oven at 105 o C for 3 hrs or until completely dried.
Step 7. Transfer the filter paper containing dried precipitates in a dessicator for 30 minutes to absorb the moisture during cooling.
Step 8. Weigh the filter paper containing the dried precipitates using analytical balance.
Step 9. Compute for the weight of the precipitates by difference.
Step 10. Compute for the % lead in wastewater.
Below are the data gathered during the experiment :
| Trial 1 | Trial 2 |
Trial 3 |
|
| Volume of sample | 10mL | 10mL |
10mL |
| Volume of added distilled water |
90mL | 90mL |
90mL |
| Volume of sodium sulfate |
9mL | 9mL |
9mL |
| Weight of filter paper |
1.06 g | 1.08 g |
1.07 g |
| Weight of filter paper + evaporating dish + precipitate after drying |
35.6525 | 35.6565 |
35.2351 |
| Weight of evaporating dish | 34.4306 | 34.4325 |
33.9914 |
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