How metals react with water and oxygen. Give equations.
Answers
Answer:
Group 1: Alkali Metals
A common characteristic of most Alkali Metals is their ability to displace H2(g) from water. This is represented by their large, negative electrode potentials. In this event, the Group 1 metal is oxidized to its metal ion and water is reduced to form hydrogen gas and hydroxide ions. The general reaction of an alkali metal (M) with H2O (l) is given in the following equation:
2M(s)+2H2O(l)⟶2M+(aq)+2OH−(aq)+H2(g)(1)
From this reaction it is apparent that OH- is produced, creating a basic or alkaline environment. Group 1 elements are called alkali metals because of their ability to displace H2(g) from water and create a basic solution.
Alkali metals are also known to react violently and explosively with water. This is because enough heat is given off during the exothermic reaction to ignite the H2(g).
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Figure 1 : Reactivity of Lithium (top), sodium (middle) and potassium (bottom) metals and water. (Free for Educational Use only, chemlegin).
Alkali Metals Oxides and Water
Oxides of Group 1 elements also react with water to create basic solutions. Alkali metals react with oxygen to form monoxides, peroxides, or superoxides. These species react with water in different ways:
Monoxides (M2O) produce alkali metal hydroxides:
M2O(s)+2H2O(l)⟶2M+(aq)+2OH−(aq)(2)
Peroxides (M2O2) produce metal hydroxides and hydrogen peroxide:
M2O2(s)+2H2O(l)⟶2M+(aq)+2OH−(aq)+H2O2(aq)(3)
Superoxides (MO2) produce metal hydroxides, hydrogen peroxide, and oxygen gas:
2MO2(s)+2H2O(l)⟶2M+(aq)+2OH−(aq)+H2O2(aq)+O2(g)(4)
Alkali Metal Hydrides and Water
Similarly to the Group 1 oxides, the hydrides of the Group 1 elements react with water to form a basic solution. In this case, however, hydrogen gas is produced with the metal hydroxide. The general reaction for alkali metal hydrides and water is given below:
MH(s)+H2O(l)⟶M+(aq)+OH−(aq)+H2(g)(5)
This reaction can be generalized to all alkali metal hydrides.
Group 2: Alkaline Earth Metals
The majority of Alkaline Earth Metals also produce hydroxides when reacted with water. The hydroxides of calcium, strontium, and barium are only slightly soluble in water; however, enough hydroxide ions are produced to make a basic environment. The general reaction of calcium, strontium, and barium with water is represented below, where M represents calcium, strontium, or barium:
M(s)+2H2O(l)⟶M(OH)2(aq)+H2(g)(6)
Magnesium (Mg) reacts with water vapor to form magnesium hydroxide and hydrogen gas. Beryllium (Be) is the only alkaline earth metal that does not react with water. This is due to its small size and high ionization energy in relation to the other elements in the group.
Alkaline Earth Metal Oxides and Water
Similarly to the alkali metal oxides, alkaline earth metal monoxides combine with water to form metal hydroxide salts (as illustrated in the equation below). The exception to this general assumption is beryllium, whose oxide (BeO) does not react with water.
MO(s)+H2O(l)⟶M(OH)2(s)(7)
One of the most familiar alkaline earth metal oxides is CaO or quicklime. This substance is often used to treat water and to remove harmful SO2(g) from industrial smokestacks.
Alkaline Earth Metal Hydrides and Water
With the exception of beryllium (Be), the alkaline metal hydrides react with water to produce the metal hydroxide and hydrogen gas. The reaction of these metal hydrides can be described below:
MH2(s)+2H2O(l)⟶M(OH)2(aq)+2H2(g)(8)
Explanation:
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Most metals form oxides with the oxygen in a -2 oxidation state. As a general rule, metal oxides are basic and nonmetal oxides are acidic. ... Oxygen also forms covalent oxides with non-metals, that react with water to form acidic solutions