IV. Procedure Cut an approximate 5 cm. square of aluminum from an aluminum can,

Question

IV. Procedure Cut an approximate 5 cm. square of aluminum from an aluminum can, and beaker must be clamped screen scour only the painted outside of it with coarse steel wool ring support to scrape off all paint. Cleaning the aluminum well now, right down to the shiny metal, will avoid problems later on. The plastic coating on the inside will easily come off in one piece if you do not scour it at all. Find and record the exact mass, to 0.001 g, of the piece of aluminum;it should weigh about 0.5 gram. Figure &-1 Add the weighed aluminum to a 250 mL beaker, then clamp the beaker down onto a wire sereen over a ring at your bench. Next, add 50 mL of 2 M potassium hydroxide, KOH to the beaker. (Caution: strong base is quite caustic and will eat holes in clothing and in you! Do not spatter!) Use a small Bunsen burner to heat gently with a small flame. Unstable set-ups will not be tolerated, and a wire screen is absolutely necessary to prevent the beaker from spot heating and cracking. Turn on the lab's hoods and fans, and open windows. Gently boil until the liquid is concentrated to one-half its original level. Do NOT e more because spattering can occur. If the level drops below this, simply add more water to bring the level up. If foaming is an issue, you are heating too strongly, and you need to lower the heat source or pullit further from the beaker. When the plastic backing comes off, use tongs to raise the plastic above the hot solution, deionized water. Then place it on paper towels and blot dry; set it aside to dry further. If the solution is not clear and contains suspended solids, filter the hot solution (caution!) through a thin plug of glass wool that is moistened by pouring 2 mL of deionized water through it (Figure 8-2). After filtering, rinse the glass wool with 1 mL or less of DI water to minimize loss of product. and rinse it with After the plastic backing has dried, weigh the plastic and deduct this mass from the original mass of the aluminum piece to get the mass of just the aluminum metal.

Explanation / Answer

Step 1: cut a piece of aluminium from aluminium can. Remove the plastic coating from the piece and then weigh.

Step 2: weighed aluminium is added to a 50 mL beaker and clamp the beaker down onto a wire screen over a ring. Now we have to add 50 mL of 2M KOH to the beaker. Boil the mixture until the liquid is concentrated to one-half its original level.

Step 3: back the plastic to raise the plastic above the hot solution. After drying plastic backing, we have to weigh the plastic. Let us deduct the mass of plastic from the original mass of aluminium piece.

Ste 4: cool the solution and add 20mL of 9 M H2SO4 with constant stirring. Aluminium hydroxide will form; aluminium hydroxide will dissolve, when we heat the solution gently. Solution must be clear after heating.

Step 5: cool the clear solution in an ice bath for 20-25 min. alum crystals will form. Filter the solution to separate the crystals from the solution by vacuum filtration. Dry the crystals and then weigh.

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