0.3 Going green with al  (Page 3/3)

Sample #2 (Group B)

Part 1: Preparation of Alum

1. Cut a 5cm x 5cm square piece of aluminum from a scrap aluminum can and sand the paint off using steel wool.
2. Cut this piece into smaller pieces (about 0.5 cm long) and weigh out ~0.5 g. Record the weight to 3 decimal places.
3. Place the aluminum in a 400-mL beaker and add 25 mL of 4 M KOH.
4. Place beaker on the heating mantle and heat gently.

CAUTION - H 2 GAS (VERY EXPLOSIVE) IS PRODUCED.ENSURE THAT YOU ONLY HEAT THE BOTTOM OF THE BEAKER

1. When the bubbles have stopped, all of the aluminum will have reacted. Remove from the heat temporarily

Part 2: Calculation of Percent Yield

1. Vacuum filter the solution. This is done by taking a filter funnel, placing a piece of wet filter paper in it, placing the funnel in a vacuum flask, and attaching the flask to the vacuum line, labeled “vac” on the outlet taps . Save the filtrate (the liquid inside the filter flask). You may dispose of the solid in the marked waste beaker.
2. Clean the 400 mL beaker you used before and pour the filtrate into it.
3. Carefully, rinse your 100 mL graduated cylinder. Dispense 15 mL of 3 M H ₂ SO ₄ into it, which you will then add to the filtrate.

CAUTION - H 2 SO 4 IS A STRONG ACID AND DEHYDRATOR.  SEE TA IMMEDIATELY IF YOU SPILL ANY! 

USE EXTREME CAUTION WHEN CLEANING YOUR GRADUATED CYLINDER AFTER IT HAS COME INTO CONTACT WITH THE SULFURIC ACID. BE SURE TO WEAR GLOVES WHILE HANDLING IT AT ALL TIMES!!

1. Heat gently while stirring until the solution becomes clear. Add 2 or 3 boiling chips, and boil the solution down to a volume of 20 mL. Do not boil the solution to dryness.
2. After "boiling off", let the beaker cool to room temperature. Crystals of alum should form. Allow to cool for 15 minutes, or until crystals are clearly visible. Disregard any tiny black specks.
3. Once you see that the crystals are clearly formed, vacuum filter the product and wash the beaker and then the product in the funnel with a small amount of ethanol to remove any remaining crystals from the beaker and remove any impurities.
4. Transfer the remaining solid to a watch glass, scraping the filter paper with a spatula to remove as much of the product as possible.
5. Place the watch glass in the drying oven at 40 or 50 degrees (your TA should adjust this) for 10 to 15 minutes, until the white solid appears dry.
6. Remove the boiling chips and weigh.
7. Using the initial mass of aluminum and the mass of your solid, calculate the percent yield and describe the appearance of the crystals.
8. Dispose of the alum in the marked waste beaker.

Both Groups A&B 

Part 3: Acid-Base Properties of Aluminum Compounds

1. Clean two test-tubes and label them 1 and 2. Place 10 drops of 1M aluminum nitrate solution in each tube. Add 10 drops of 1.0 M sodium hydroxide solution to each tube, mix well, and record your observations on your lab report.
2. Add 3 mL of 6M sodium hydroxide solution to tube 1. Mix well and record your observations.
3. Add 3 mL of 6M HCl solution to tube 2. Mix well and record your observations.
4. To tube 1, add aluminum hydroxide (the product from step 9 of Group A’s prep of alum), 3 mL of 6M ammonium hydroxide, i.e. aqueous ammonia and record your observations.
5. Dispose of solutions in the waste beaker in the hood.