When either chlorine or hydrogen chloride is passed over a heated metal M, the same chloride is produced. An aqueous solution of this chloride is acidic. Which one of the following could be M?
A: Al
B: Ba
C: Cu
D: Fe
E: Na
Ans: A
Help w explanation please! Thanks!
Poor question. NaCl is the only one of those listed that would not be, at least slightly, acidic.
AlCl3, BaCl2, CuCl2 and FeCl2 all would be at least slightly acidic. AlCl3 would be the most acidic because it's a more active metal than the others. Why are they acidic? Becasue they hydrolyze with H2O. Al as follows:
AlCl3 + 3HOH ==> Al(OH)3 + 3HCl.
It's easier to write this way but it is more accurate to depict it as
Al(H2O)6(^3+ charge) + H2O ==> H3O^+ + Al(H2O)5(OH^-)^2+
To determine which metal M could produce an acidic solution when reacted with both chlorine and hydrogen chloride, we need to consider the reactivity of the metals and their ability to form chlorides.
First, let's start with the reaction of chlorine gas (Cl2) with metals. When metal reacts with chlorine, it undergoes a redox reaction where the metal is oxidized and loses electrons, while chlorine is reduced and gains electrons. The resulting product is a metal chloride.
Similarly, when hydrogen chloride gas (HCl) reacts with metals, the metal reacts with the hydrogen ions (H+) from HCl to form the corresponding metal chloride.
Now, we know that the aqueous solution of this chloride is acidic. An acidic solution implies the presence of H+ ions. In this case, the H+ ions are derived from the reaction of the metal with hydrogen chloride. The more reactive the metal is, the stronger the acid it will produce.
Out of the given options, only Aluminum (Al) is reactive enough to produce an acidic solution when reacted with both chlorine and hydrogen chloride. Aluminum forms aluminum chloride (AlCl3), which, when dissolved in water, dissociates to release H+ ions, resulting in an acidic solution.
Therefore, the correct answer is A: Al.