Answer: 3
Explanation:
An oxide-reduction reaction or, simply, redox reaction, is a <u>chemical reaction in which one or more electrons are transferred between the reactants</u>, causing a change in their oxidation states, which is the hypothetical electric charge that the atom would have if all its links with different elements were 100% ionic.
For there to be a reduction-oxidation reaction, in the system there must be an element that yields electrons and another that accepts them:
-
The oxidizing agent picks up electrons and remains with a state of oxidation inferior to that which it had, that is, it is reduced.
- The reducing agent supplies electrons from its chemical structure to the medium, increasing its oxidation state, ie, being oxidized.
To balance a redox equation you must <u>identify the elements that are oxidized and reduced and the amount of electrons that they release or capture, respectively.
</u>
In the reaction that arises in the question the silver (Ag) is reduced <u>because it decreases its oxidation state from +1 to 0</u> and the aluminum (Al) is oxidized because <u>its oxidation state increases from 0 to +3</u>, releasing 3 electrons (e⁻). Then we can raise two half-reactions:
Ag⁺ + e⁻ → Ag⁰
Al⁰ → Al⁺³ + 3e⁻
In order to obtain the balanced equation, we must multiply the first half-reaction by 3 so that, when both half-reactions are added, the electrons are canceled. In this way:
(Ag⁺ + e⁻ → Ag⁰ ) x3
Al⁰ → Al⁺³ + 3e⁻ +
-------------------------------------
3Ag⁺ + Al⁰ → 3Ag⁰ + Al⁺³
So, the coefficient of silver in the final balanced equation is 3.
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