Amphoteric Oxides - Identification, Examples, & Faq’s
ChemistryArticles
Oxides can be divided into acidic, basic, amphoteric, or neutral.AnAmphoteric Oxide is an oxide that can act as either an acid or a base. In general, non-metal oxides are acidic, and metal oxides are basic. Some non-metallic oxides are neutral, and some metallic or semi-metallic oxides are amphoteric. There are several exceptions to these generalizations.
Table of Content
● What areAmphoteric Oxides?
● Identification ofAmphoteric Oxides
● Oxides of group 13 elements
● Amphoteric Oxides Examples
● Amphoteric Oxides in PeriodicTable
● FrequentlyAsked Question (FAQs)
What areAmphoteric Oxides?
Amphoteric Oxides are the oxides that act as acidic and basic oxides. It has features of acidic oxide and basic oxides that neutralize both acids and bases.
Amphoteric oxides generally dissolve in water to form alkaline solutions. TheAlkaline solutions consist of hydroxide ions. Therefore, aluminum oxide (Al2O3) reacts with hydrochloric acid to form aluminum chloride and water The sodium hydroxide solution forms water and sodium aluminate (NaAlO2). Other examples of amphoteric oxides include ZnO, SnO, and PbO.
Identification ofAmphoteric Oxides
Oxides are compounds of metals or nonmetals with oxygen. There are 4 types of oxides.Amphoteric oxides are categorized as metal oxides that react with both acids and bases to form water and salts.Amphoteric oxides, among many others, include zinc oxide and lead oxide. Examples include amino acids and proteins with amine and carboxylic acid classes and molecules that can self-ionize, such as water
Amphoteric oxides are oxygen compounds that exhibit both acidic and basic properties. These oxides undergo a neutralization reaction to form water and salt when they react with acid.This demonstrates the basic properties of compounds. Similarly, alkali reacts to form salt and water, which has an acidic property. Example: aluminum oxide.
All oxides can be formed by heating the element in oxygen. By reacting aqueous solutions of metal trihalides with hydroxide, oxides are obtained in hydrated form. Descending in the group, there is a transition from acid oxides to amphoteric to basic oxides due to the increasing metallic character of the respective elements.
Oxides of group 13 elements
Oxides Properties
B2O3
Al2O3
Ga2O3
Weakly acidic
Amphoteric
Amphoteric
In2O3 Weakly base
Tl2O3 Basic, oxidizing
Amphoteric Oxides Examples
The term amphoteric means both acid and base.Amphoteric oxides have both acidic and basic properties. Examples are aluminum and zinc oxides. When reacting with acids, they form salts. They also react with alkalis to form complex salts.
Examples:
ZnO(s) + 2HNO3(aq) → Zn(NO3)2(aq) + H2O(l)
ZnO(s) + 2NaOH(aq) → Na2ZnO2(aq) + H2O(l)
Al2O3(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2O(l)
Al2O3(s) + 2NaOH(aq) → 2NaAlO2(aq) + H2O(l)
Both the Zincates and aluminates have the ending -ate to indicate that their ions are complex ions containing oxygen - rather like sulfates, carbonates, and nitrates, meaning that the ions are ZnO22- and the aluminate ions are AlO2- The ions are written as Zn(OH)42- andAl(OH)4-. Note that sodium zincate and aluminate are soluble in water
Amphoteric Oxides in Periodic Table
In a given period, oxides progress from strongly basic, weakly basic, amphoteric, and weakly acidic to strongly acidic, e.g., Na2O, MgO, Al2O3, P4O10, SO3, and Cl2O7.Acidity increases with increasing oxidation state, e.g., MnO < Mn2O3 < Mn2O7.
There is a trend in the acidity of oxides in the periodic table. Generally, the period's trend is basic → amphoteric, → acidic. The following table shows the trend of oxide acidity for period 3.
Na2O MgO Al2O3 SiO2 P4O18 SO2 Cl2O7
Strongly basic Basic Amphoteric Weakly acidic Acidic Acidic Strongly acidic
The basic oxides are found near the bottom of groups I and II. Basicity tends to increase in the periodic group. For group V, the acidities of the oxides are NO2 (acidic), P2O3 (acidic), andAs2O3 (amphoteric). Sb2O3 (amphoteric), Bi2O3 (basic).
In the main groups of elements, the basicity of oxides increases with an increasing atomic number in the group, e.g., BeO < MgO < CaO < SrO < BaO, although the trend is reversed in the later groups of transition elements.
FrequentlyAsked Questions (FAQs)
Q1. How do you know if the oxide is amphoteric?
Ans.You may say that if an oxide reacts with acid and forms a salt, or if an oxide reacts with a base and forms a salt, then you can say that it is an amphoteric oxide.
Q2. Which elements form amphoteric oxides?
Ans. Metals such as zinc, copper, tin, lead, aluminum, and beryllium form amphoteric oxides or hydroxides.
Q3. How many oxides are amphoteric in nature?
Ans.Aluminum, beryllium, tin, and zinc oxide are all amphoteric.
Q4. Is CO2 amphoteric?
Ans. No, CO2 is acidic in nature.
Q5. Is NaOH amphoteric?
Ans. No.Alkali metals' hydroxides and oxides do not show amphoteric properties. Therefore NaOH is not an amphoteric compound.
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