Youhydrides (YH) are binary substances that have hydrogen as a chemical element plus electronegative. The following elements may be part of its composition:
IA (alkali metals);
IIA (alkaline earth metals);
Aluminum;
Semimetals or non-metals less electronegative than hydrogen.
In relation to its composition, hydrides can be classified into:
ionic hydrides (formed by representative metals);
Molecular hydrides (formed by semimetals or non-metals with low electronegativity);
interstitial hydrides (formed by transition metals).
Knowing the composition and classification of a hydride is critical in determining whether it is a compound capable of undergoing a chemical reaction or not. Whenever a metal hydride is mixed with water, the products generated by this process are an inorganic base and hydrogen gas (H2).
NOTE: The hydride reaction with water only forms base inorganic when the hydride contains a metal.
The chemical equation of a hydride reaction with water can be represented as follows:
YH + H2O → YOH + H2
THE inorganic base formed by the reaction of a hydride with water it depends on the metal that is part of its composition.
Here are some examples of this type of reaction:
Example 1: Sodium hydride (NaH)
NaH + H2O → ?
Sodium hydride presents alkali metal sodium (NOX +1). this one, when interacting with the hydroxide (oh-1) present in water, forms sodium hydroxide (NaOH).
The base formed will have the formula NaOH because, in the construction of the formula of an ionic compound, we must perform the crossing of the charges of the cation and the anion. However, how the charges have the same numerical value (1), in this example, the crossover is not performed.
NaH + H2O → NaOH + H2
In this equation, it was not necessary to carry out the balancing, because the amounts of Na, H and O in the reactants and products were already equal.
Example 2: calcium hydride (CaH2)
CaH2 + H2O → ?
Calcium hydride has the alkaline earth metal calcium (NOX +2). this one, when interacting with the hydroxide (oh-1) present in water, forms calcium hydroxide [Ca(OH)2].
The base formed will have the formula Ca(OH)2 because, in the construction of the formula of an ionic compound, we must cross the charges of the cation and the anion. In this way, the calcium charge (+2) becomes the amount of hydroxyl (OH), and the hydroxide charge (-1) becomes the amount of calcium.
CaH2 + 2 H2O → Ca(OH)2 + 2 H2
In this equation, it was necessary to carry out the balancing, because the amounts of Ca, H and O in the reactants and products were not equal. For this, we put coefficient 2 in the water formula and coefficient 2 in the H formula2, thus equaling the amounts of Ca, H and O in the reactants and products.
Example 3: aluminum hydride (AlH3)
AlH3 + H2O → ?
Aluminum hydride features the aluminum metal, belonging to the IIIA family(NOX +3). this one, when interacting with the hydroxide (oh-1) present in water, forms calcium hydroxide [Al(OH)3].
The base formed will have the formula Al(OH)3 because, in the construction of the formula of an ionic compound, we must cross the charges of the cation and the anion. In this way, Aluminum charge (+3) becomes the amount of hydroxyls (OH), and the hydroxide charge (-1) becomes the amount of Aluminum.
AlH3 + 3 H2O → Al(OH)3 + 3 H2
In this equation, it was necessary to carry out the balancing. For this, we put coefficient 3 in the formula for water and coefficient 3 in the formula for H2, thus equaling the amounts of Al, H and O in the reactants and products.
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/quimica/reacoes-hidretos-com-agua.htm