Using an aluminum can, a student dissolves the aluminum in concentrated potassiu

Question

Using an aluminum can, a student dissolves the aluminum in concentrated potassium hydroxide. This process is accompanied by the evolution of large amounts of hydrogen gas and the soluble complex, potassium tetrahydroxoaluminate. After filtering away the undissolved paint and plastic coating, the student acidifies the solution with sulfuric acid. Upon cooling the solution, white crystals of "alum flour", KAl(SO4)2•12H2O, form. How many liters of hydrogen gas (at STP) are produced when a 27.0 g sample of aluminum metal reacts to produce tetrahydroxoaluminate ion

Explanation / Answer

In the reaction, 2 moles of Al reacts to give 3 moles of H2 gas

moles of Al used = 27 g/26.98 g/mol = 1.00 mols

So moles of H2 produced = 1 x 3/2 = 1.5 mols

Volume of H2 produced = 1.5 x 22.4 = 33.6 L

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