CHEMICAL ALERT copper(ll) sulfate-toxic and irritant 95% ethanol-flammable and h

Question

CHEMICAL ALERT copper(ll) sulfate-toxic and irritant 95% ethanol-flammable and highly toxic 6M hydrochloric acid-toxic, corrosive, and moisture sensitive 3% hydrogen peroxide solution-corrosive and oxidant 3M potassium hydroxide-toxic and corrosive 4M sulfuric acid-corrosive and toxic CAUTION Wear departmentally approved eye protection while doing this experiment. A. Dissolving Al Foil in Basic Solution Determine the mass of a piece of weighing paper. Record this mass on Data Sheet 1. Cut or tear 1 x 1-cm pieces of Al foil. Transfer foil pieces onto the weighing paper until the mass of the foil is 0.450-0.500 g. Record the exact mass of the foil plus weighing paper on Data Sheet 1. Transfer the foil into a clean 150-mL beaker labeled with your initials. Hydrogen, a flammable gas, is a product of the reaction between 3M KOH solution and Al foil. Your laboratory instructor will tell you whether or not to carry out this step under a fume hood. The reaction starts slowly because the KOH must first dissolve the protective coating on the foil. Once the Al is exposed, the reaction becomes vigorous and highly exothermic.

Explanation / Answer

The observations that indicate that the Al foils has a protective coating are,

1. Aluminium is very reactive in air and forms a protective oxide coating. This protects it when placed in water as aluminium oxide is unreactive with water.

2. When immersed in mercury the oxide coating is removed and therefore the aluminium itself reacts when the cleaned aluminium metal is immersed in water.

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