What are Nonmetal Oxides?
All the nonmetals form covalent oxides with oxygen that react with water to produce acids or with bases to produce salts. The majority of nonmetal oxides are acidic, forming oxyacids, which contain hydronium ions (H3O+) in aqueous solutions.
There exist two general statements, which describe the acidic oxide behaviour. The oxides, such as dinitrogen pentoxide (N2O5) and sulphur trioxide (SO3), are called acid anhydrides because the nonmetal exhibits one of its typical oxidation numbers.
Reactions of Nonmetal Oxides
Nonmetal oxides react with water to produce oxyacids, with no change in the nonmetal’s oxidation number. For example:
N2O5 + H2O → 2HNO3
Second, metal oxides that do not have one of the metal's typical oxidation numbers, such as nitrogen dioxide (NO2) and chlorine dioxide (ClO2), react with water as well. The nonmetal, on the other hand, is both oxidised and reduced in these reactions (i.e., its oxidation number is increased and decreased, respectively). A disproportionation reaction occurs when the same element is oxidised and reduced at the same time. N0+ is reduced to N2+ (in NO) and oxidised to N5+ in the next disproportionation reaction (in HNO3).
3NO2 + H2O → 2HNO3 + NO
Oxides of Nitrogen
The oxides are formed by nitrogen (N), which exhibit each of its positive oxidation numbers ranging from +1 to +5. Nitrous oxide (or dinitrogen oxide), N2O, is formed when the ammonium nitrate (NH4NO3) is heated. This colorless gas has a nice and mild odor and a sweet taste and is used as a local anesthetic for minor procedures, especially in dentistry. It is also called laughing gas due to its intoxicating effect. And, it is used widely as a propellant in aerosol cans of whipped cream.
Nitric oxide (NO) is created in many ways. The lightning that takes place during thunderstorms brings up the direct union of oxygen and nitrogen in the air to form fewer amounts of nitric oxide, as does heating these two elements together. Nitric oxide can be produced commercially by burning ammonia (NH3), but it can also be made in the lab by reducing dilute nitric acid (HNO3) with, for example, copper (Cu).
3Cu + 8HNO3 → 2NO + 3Cu(NO3)2 + 4H2O
Oxides of Phosphorus
Phosphorus
(III) oxide (also known as tetraphosphorus hexoxide), P4O6, and phosphorus (V) oxide (also known as tetraphosphorus decaoxide), P4O10, are two popular oxides. Both these oxides contain a structure based on the tetrahedral structure of the elemental white phosphorus. Phosphorus(III) oxide comes in the form of a white crystalline solid with a garlic-like odor and a poisonous vapor. It oxidizes slowly in the air and flames when heated to 70°C (158°F) by forming P4O10. It is phosphoric acid (H3PO3) acid.
anhydride, produced as P4O6, that dissolves slowly in cold water. Phosphorus(V) oxide is a white flocculent powder made by heating elemental phosphorus in the presence of excess oxygen. It is a poor oxidizing agent and is very stable. The molecule P4O10 is an acid anhydride of H3PO4, an orthophosphoric acid. When this P4O10 is dropped into water, heat is liberated, the acid is formed and makes a hissing sound. Due to its great affinity for water, P4O10 can be used extensively as a drying agent for the gasses and to remove water from several compounds.
P4O10 + 6H2O → 4H3PO4
Oxides of Carbon
Carbon forms two well-known oxides, which are carbon monoxide (CO), and carbon dioxide (CO2). In addition, it also forms C3O2 and carbon suboxide.
Carbon Monoxide
Carbon monoxide can be produced when graphite (a naturally occurring form of elemental carbon) is burned or heated in a limited amount of oxygen. Steam with red-hot coke reaction also produces carbon monoxide, including hydrogen gas (H2). Coke is given as an impure carbon residue resulting from coal burning.
This CO and H2 mixture is called water gas and can be used as an industrial fuel. In the laboratory, carbon monoxide can be prepared by heating the oxalic acid (H2C2O4) or formic acid (HCOOH) with the conc. sulfuric acid (H2SO4). The sulfuric acid removes the water elements (it means H2O) from the oxalic or formic acid and absorbs the produced water because the carbon monoxide burns readily in oxygen to form carbon dioxide,
2CO + O2 → 2CO2
It is also useful as a gaseous fuel and as a metallurgical reducing agent because it reduces several metal oxides to the elemental metal at high temperatures. For example, iron (III) oxide (Fe2O3) and copper (II) oxide (CuO) are both reduced to metal by the carbon monoxide compound.
Carbon Dioxide
Carbon dioxide can be produced when almost any carbon compound or any form of carbon is burned in excess oxygen. Several metal carbonates liberate CO2 when heated. Calcium carbonate (CaCO3), for example, contains calcium oxide (CaO) and carbon dioxide.
CaCO3 + heat → CO2 + CaO
How to Prepare Notes on Non-Metal Oxides?
Go through Nonmetal Oxides - Reactions, Oxides of Nitrogen, Carbon, and FAQs on Vedantu.
Read from this page and try to understand the explanations provided.
Re-read those portions that seem a bit unclear towards the beginning.
Write down everything in an organized manner.
Keep your sentences brief and to the point.
Highlight all the key parts using a coloured pen.
Use drawings if possible to retain the concepts.
Revise from here before appearing for a test on Non-metal oxides.
How Does Vedantu Prepare Students for a Chemistry Test on Metal Oxides ?
Vedantu has appropriate study material on Metal oxides that students can read from. They can check out Nonmetal Oxides on Vedantu and then understand the topic better. The definition and reactions with the other oxides have been explained here. Studying from this section will help students secure higher marks in their exams as the material present here is relevant and in keeping with the Chemistry syllabus.
FAQs on Nonmetal Oxides
1. What are non-metal oxides?
A non-metal oxide is a chemical compound formed when a non-metallic element reacts with oxygen. These compounds are typically characterised by covalent bonds. When dissolved in water, most non-metal oxides form acidic solutions, or they react with bases to produce salt and water. For more details, you can refer to the page on Nonmetal Oxides.
2. What are some common examples of non-metal oxides?
There are numerous non-metal oxides that are fundamental in chemistry. Some common examples include:
- Carbon Dioxide (CO₂): A key component in respiration and a greenhouse gas.
- Sulfur Dioxide (SO₂): A precursor to acid rain and used as a preservative.
- Sulfur Trioxide (SO₃): Used in the industrial production of sulfuric acid.
- Nitrogen Dioxide (NO₂): A brown, toxic gas and a major air pollutant.
- Dinitrogen Monoxide (N₂O): Also known as laughing gas, used in medical and dental procedures.
3. Why are most non-metal oxides acidic in nature?
Most non-metal oxides are considered acidic anhydrides because they react with water to form an acid. When a non-metal oxide like carbon dioxide (CO₂) dissolves in water (H₂O), it forms carbonic acid (H₂CO₃). This acid then dissociates in water to release hydrogen ions (H⁺), which is the defining characteristic of an acid. Similarly, sulfur trioxide (SO₃) reacts with water to form the strong acid, sulfuric acid (H₂SO₄). This acidic nature is why they readily react with bases in a neutralisation reaction. You can learn more about this in our notes on Acids, Bases and Salts.
4. How do non-metal oxides differ from metal oxides?
The primary differences between non-metal and metal oxides lie in their bonding and chemical properties:
- Nature of Bonding: Non-metal oxides typically have covalent bonds, as they are formed between two non-metallic elements. In contrast, metal oxides usually have ionic bonds due to the large electronegativity difference between the metal and oxygen.
- Chemical Nature: Non-metal oxides are generally acidic or neutral. Metal oxides are predominantly basic, although some can be amphoteric (reacting as both an acid and a base).
- Reaction with Water: Non-metal oxides react with water to form acids (e.g., SO₂ forms sulfurous acid). Metal oxides react with water to form basic hydroxides (e.g., Na₂O forms sodium hydroxide). For a detailed comparison, see the Chemical Properties of Metals and Non-metals.
5. What happens when a non-metal oxide reacts with a base? Provide an example.
When an acidic non-metal oxide reacts with a base, it undergoes a neutralisation reaction to form a salt and water. This reaction is analogous to a classic acid-base reaction.
For example, when carbon dioxide (CO₂, an acidic oxide) is passed through a solution of sodium hydroxide (NaOH, a strong base), it forms sodium carbonate (Na₂CO₃, a salt) and water (H₂O).
The chemical equation is: CO₂(g) + 2NaOH(aq) → Na₂CO₃(aq) + H₂O(l). You can explore more about this in the topic Reaction of Non-Metallic Oxide with Base.
6. Are all non-metal oxides acidic? Explain with examples.
No, not all non-metal oxides are acidic. While many are, there is an important class of oxides known as neutral oxides. These oxides do not react with either acids or bases. They are essentially chemically inert in this context.
Key examples of neutral oxides include:
- Carbon Monoxide (CO)
- Nitrous Oxide (N₂O)
- Nitric Oxide (NO)
7. What are the main types of oxides found in chemistry?
Oxides are broadly classified into four main types based on their acid-base characteristics:
- Acidic Oxides: Typically formed by non-metals (e.g., SO₂, CO₂). They react with bases to form salt and water.
- Basic Oxides: Typically formed by metals (e.g., CaO, Na₂O). They react with acids to form salt and water.
- Amphoteric Oxides: These can act as both acidic and basic oxides. They are usually formed by metalloids or some metals like zinc and aluminium (e.g., Al₂O₃, ZnO).
- Neutral Oxides: These show neither acidic nor basic properties (e.g., CO, N₂O).
This classification of oxides helps in predicting their chemical behaviour.
8. How does the acidic character of non-metal oxides change in the periodic table?
The acidic character of non-metal oxides follows predictable periodic trends:
- Across a Period: Moving from left to right across a period, the electronegativity of the non-metal increases. A higher electronegativity pulls the electron density more strongly, making the O-H bond in the resulting acid more polar and easier to break, thus increasing the acidic strength of the oxide. For example, the acidity of oxides increases in the order SiO₂ < P₄O₁₀ < SO₃ < Cl₂O₇.
- Down a Group: Moving down a group, the electronegativity of the central non-metal atom decreases. This leads to a decrease in the acidic strength of the oxides. For example, among the oxides of Group 15, the acidic character decreases from N₂O₅ to Bi₂O₃.
These trends are a key concept in understanding the periodicity of properties.
9. What are the key oxides of nitrogen and their significance?
Nitrogen forms a variety of oxides due to its ability to exist in multiple oxidation states. The key oxides are:
- Nitrous Oxide (N₂O): A colourless, neutral oxide used as an anaesthetic (laughing gas) and a propellant in aerosol sprays.
- Nitric Oxide (NO): A colourless, neutral oxide that acts as an important signalling molecule in biological systems and is a key intermediate in the formation of acid rain.
- Nitrogen Dioxide (NO₂): A reddish-brown, acidic gas that is a major air pollutant from vehicle exhaust and industrial emissions. It is a crucial component of smog.
- Dinitrogen Pentoxide (N₂O₅): A white solid and a strong acidic oxide, it is the anhydride of nitric acid.
