Amphoteric Oxides - Identification, Examples, & Faq’s.pdf

Oxides can be divided into acidic, basic, amphoteric, or neutral. An Amphoteric 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.

1. Amphoteric Oxides - Identification,
Examples,& Faq’s
Chemistry Articles
Oxides can be divided into acidic, basic, amphoteric, or neutral. An Amphoteric 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.

2. Table of Content
●What are Amphoteric Oxides?
●Identification of Amphoteric Oxides
●Oxides of group 13 elements
●Amphoteric Oxides Examples
●Amphoteric Oxides in Periodic Table
●Frequently Asked Question (FAQs)
What are Amphoteric 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. The Alkaline
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 examplesof amphoteric oxides
include ZnO, SnO, and PbO.
Identification of Amphoteric 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.

3. Oxides of group 13 elements
Oxides Properties
B2O3 Weakly acidic
Al2O3 Amphoteric
Ga2O3 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 areAlO2-. The ions are written as
Zn(OH)42-and Al(OH)4-. Note that sodium zincate andaluminate 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.

4. 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 MgOAl2O3 SiO2 P4O18SO2Cl2O7
Strongly
basic
BasicAmphotericWeakly
acidic
AcidicAcidicStrongly
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), and As2O3(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.
Frequently Asked 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 CO2amphoteric?
Ans. No, CO2is 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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