Write the chemical equation for the following statement.
Steam is passed over aluminum.
A) $A l + H_{2} O \to A l_{2} (O H)$
B) $2 A l + 3 H_{2} O \to A l_{2} O_{3} + 3 H_{2}$
C) $2 A l + 9 H_{2} O \to A l_{2} O_{3} + 3 H_{2}$
D) $2 A l + 8 H_{2} O \to A l_{2} O_{3} + 3 H_{2}$

Answer

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Hint: We must have to know that when steam is passed over aluminum; aluminum reacts with steam to form aluminum oxide and hydrogen gas. As we know that aluminum is a chemical element with the symbol

A l

and atomic number

13

. Aluminum has a density lower than those of other common metals, at approximately one third that of steel.

Complete answer:
We will look at all the options one by one:
Option A) this option is incorrect as the product in this reaction has an incorrect chemical formula.
Option B) this option is correct as Aluminum oxide is formed in the beginning and it forms a protective layer on the aluminum and stops the reaction. But on increasing the temperature further, the protective coating breaks evolving hydrogen again.
So we can write the correct chemical equation that defines the reaction between steam and aluminum as,

2 A l + 3 H_{2} O \to A l_{2} O_{3} + 3 H_{2}

Option C) this option is incorrect as the chemical equation is not balanced.
Option D) this option is incorrect as the chemical equation is not balanced.

Option B is the correct answer.

Note:
As we know, an aluminum atom has

13

electrons, arranged in an electron configuration of

[N e] 3 s^{2} 3 p^{1}

with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminum are far lower than the fourth ionization energy alone. We have to remember that the steam is water in the gas phase. Steam that is saturated or superheated is invisible; however, "steam" often refers to wet steam, the visible mist or aerosol of water droplets formed as water vapor condenses.