What is the type of reaction in which two or more reactants combine to a give a single 3 2 product?

A wheel rim is not very useful by itself. Driving on the rim can damage it and make for a very rough ride. When the rim is combined with a tire, the product can be put on a car and used for a safe and comfortable ride. The two separate items combine to make something that improves the car ride.

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Table of Contents
1. Combination Reaction
2. Decomposition Reaction
3. Displacement Reaction
4. Double Displacement Reaction
5. Precipitation Reaction

A combination reaction is a reaction in which two or more substances combine to form a single new substance. Combination reactions can also be called synthesis reactions. The general form of a combination reaction is:

\[\ce{A} + \ce{B} \rightarrow \ce{AB}\nonumber \]

One combination reaction is two elements combining to form a compound. Solid sodium metal reacts with chlorine gas to produce solid sodium chloride.

\[2 \ce{Na} \left( s \right) + \ce{Cl_2} \left( g \right) \rightarrow 2 \ce{NaCl} \left( s \right)\nonumber \]

In order to write and balance the equation correctly, it is important to remember the seven elements that exist in nature as diatomic molecules: \(\ce{H_2}\), \(\ce{N_2}\), \(\ce{O_2}\), \(\ce{F_2}\), \(\ce{Cl_2}\), \(\ce{Br_2}\), and \(\ce{I_2}\).

One sort of combination reaction that occurs frequently is the reaction of an element with oxygen to form an oxide. Metals and nonmetals both react readily with oxygen under most conditions. Magnesium reacts rapidly and dramatically when ignited, combining with oxygen from the air to produce a fine powder of magnesium oxide.

\[2 \ce{Mg} \left( s \right) + \ce{O_2} \left( g \right) \rightarrow 2 \ce{MgO} \left( s \right)\nonumber \]

Sulfur reacts with oxygen to form sulfur dioxide.

\[\ce{S} \left( s \right) + \ce{O_2} \left( g \right) \rightarrow \ce{SO_2} \left( g \right)\nonumber \]

When nonmetals react with one another, the product is a molecular compound. Often, the nonmetal reactants can combine in different ratios and produce different products. Sulfur can also combine with oxygen to form sulfur trioxide.

\[2 \ce{S} \left( s \right) + 3 \ce{O_2} \left( g \right) \rightarrow 2 \ce{SO_3} \left( g \right)\nonumber \]

Transition metals are capable of adopting multiple positive charges within their ionic compounds. Therefore, most transition metals are capable of forming different products in a combination reaction. Iron reacts with oxygen to form both iron (II) oxide and iron (III) oxide:

\[2 \ce{Fe} \left( s \right) + \ce{O_2} \left( g \right) \rightarrow 2 \ce{FeO} \left( s \right)\nonumber \]

\[4 \ce{Fe} \left( s \right) + 3 \ce{O_2} \left( g \right) \rightarrow 2 \ce{Fe_2O_3} \left( s \right)\nonumber \]

Potassium is a very reactive alkali metal that must be stored under oil in order to prevent it from reacting with air. Write the balanced chemical equation for the combination reaction of potassium with oxygen.

Solution

Make sure formulas of all reactants and products are correct before balancing the equation. Oxygen gas is a diatomic molecule. Potassium oxide is an ionic compound and so its formula is constructed by the crisscross method. Potassium as an ion becomes \(\ce{K^+}\), while the oxide ion is \(\ce{O^{2-}}\).

The skeleton (unbalanced) equation:

\[\ce{K} \left( s \right) + \ce{O_2} \left( g \right) \rightarrow \ce{K_2O} \left( s \right) \nonumber\nonumber \]

The equation is then easily balanced with coefficients.

\[4 \ce{K} \left( s \right) + \ce{O_2} \left( g \right) \rightarrow 2 \ce{K_2O} \left( s \right) \nonumber\nonumber \]

Formulas are correct and the resulting combination reaction is balanced.

Can you build a balanced, combination reaction for the formation of aluminum oxide (Al2O3)?

Answer

4Al + 3O2 → 2Al2O3

Combination reactions can also take place when an element reacts with a compound to form a new compound composed of a larger number of atoms. Carbon monoxide reacts with oxygen to form carbon dioxide, according to the equation:

\[2 \ce{CO} \left( g \right) + \ce{O_2} \left( g \right) \rightarrow 2 \ce{CO_2} \left( g \right)\nonumber \]

Two compounds may also react to form a more complex compound. A very common example is the reaction of an oxide with water. Calcium oxide reacts readily with water to produce an aqueous solution of calcium hydroxide.

\[\ce{CaO} \left( s \right) + \ce{H_2O} \left( l \right) \rightarrow \ce{Ca(OH)_2} \left( aq \right)\nonumber \]

Sulfur trioxide gas reacts with water to form sulfuric acid. This is an unfortunately common reaction that occurs in the atmosphere in some places where oxides of sulfur are present as pollutants. The acid formed in the reaction falls to the ground as acid rain.

\[\ce{SO_3} \left( g \right) + \ce{H_2O} \left( l \right) \rightarrow \ce{H_2SO_4} \left( aq \right)\nonumber \]

Figure \(\PageIndex{2}\): Acid rain has severe consequences on both natural and manmade objects. Acid rain degrades marble statues like the one on the left (A). The trees in the forest on the right (B) have been killed by acid rain. (Credit: (A) Nipik; (B) Nino Barbieri; Source: (A) http://commons.wikimedia.org/wiki/File:Acid_rain_woods1.JPG(opens in new window); (B) http://commons.wikimedia.org/wiki/File:Pollution_-_Damaged_by_acid_rain.jpg(opens in new window); License: (A) Public Domain; (B) CC BY 2.5(opens in new window))

During a chemical reaction, the substances that react are known as reactants whereas the substances that are formed during a chemical reaction are known as products. Six common types of chemical reactions are discussed below.

Different Types of Chemical Reactions – Combination, Decomposition, Combustion, Neutralization & Displacement Reactions

Types of Chemical Reactions	Explanation	General Reaction
Combination reaction	Two or more compounds combine to form one compound.	A + B → AB
Decomposition reaction	The opposite of a combination reaction – a complex molecule breaks down to make simpler ones.	AB → A + B
Precipitation reaction	Two solutions of soluble salts are mixed resulting in an insoluble solid (precipitate) forming.	A + Soluble salt B → Precipitate + soluble salt C
Neutralization reaction	An acid and a base react with each other. Generally, the product of this reaction is salt and water.	Acid + Base → Salt + Water
Combustion reaction	Oxygen combines with a compound to form carbon dioxide and water. These reactions are exothermic, meaning they give off heat.	A + O2 → H2O + CO2
Displacement reaction	One element takes place with another element in the compound.	A + BC → AC + B

Also, check ⇒ Chemistry Concept Questions and Answers

The 5 primary types of chemical reactions are:

1. Combination Reaction

A reaction in which two or more reactants combine to form a single product is known as a combination reaction.
It takes the form of X + Y → XY
Combination reaction is also known as a synthesis reaction.
Example of combination reaction: 2Na + Cl2 → 2NaCl

2. Decomposition Reaction

A reaction in which a single compound breaks into two or more simpler compounds is known as a decomposition reaction.
It takes the form of XY → X + Y
A decomposition reaction is just the opposite of a combination reaction.
Example of a decomposition reaction: CaCO3 → CaO + CO2
The reaction in which a compound decomposes due to heating is known as a thermal decomposition reaction.

3. Displacement Reaction

A chemical reaction in which a more reactive element displaces a less reactive element from its aqueous salt solution.
It takes the form X + YZ → XZ + Y
It is also called a substitution reaction
Example of displacement reaction: Zn + CuSO4 → ZnSO4 + Cu

4. Double Displacement Reaction

A chemical reaction in which ions get exchanged between two reactants which form a new compound is called a double displacement reaction.
It takes the form of XY + ZA → XZ + YA
It is also called a metathesis reaction
Example of double displacement reaction:

BaCl2 + Na2SO4 → BaSO4 + 2NaCl

5. Precipitation Reaction

A chemical reaction that involves the formation of an insoluble product (precipitate; solid) is called Precipitation reaction.
The reactants are soluble, but the product formed would be insoluble and separates out as a solid.
The chemical equation by which a chemical change is described is adequate for reaction in solutions, but for reactions of ionic compounds in aqueous solution (water), the typical molecular equation has different representations.
A molecular equation may indicate formulas of reactants and products that are not present and eliminate completely the formulas of the ions that are the real reactants and products.
If the substance in the molecular equation that is actually present as dissociated ions are written in the form of their ions, the result is an ionic equation.

A precipitation reaction occurs when a solution, originally containing dissolved species, produces a solid, which generally is denser and falls to the bottom of the reaction vessel.

The most common precipitation reactions occurring in aqueous solution involve the formation of an insoluble ionic compound when two solutions containing soluble compounds are mixed. Consider what happens when an aqueous solution of NaCl is added to an aqueous solution of AgNO3. The first solution contains hydrated Na+ and Cl− ions and the second solution, Ag+, and NO3− ions.

NaCl(s) → Na+(aq) + Cl−(aq)

AgNO3(s) → Ag+(aq) + NO3−(aq)

When mixed, a double displacement reaction takes place, forming the soluble compound NaNO3 and the insoluble compound AgCl. In the reaction vessel, the Ag+ and Cl− ions combine, and a white solid precipitated from the solution. As the solid precipitates, the Na+ and NO3− ions remain in solution.

The overall double displacement reaction is represented by the following balanced equation:

NaCl(aq) + AgNO3(aq) → AgCl(s) + NaNO3(aq)

When aqueous solutions of Pb(NO3)2 and KI are mixed, does a precipitate form?
Write a balanced equation for the precipitation reaction that occurs when aqueous solutions of copper(II) iodide and potassium hydroxide are combined.

Solution:

You are asked to predict whether a precipitate will form during a chemical reaction and to write a balanced equation for a precipitation reaction.

You are given the identity of two reactants.

1. Yes, a solid precipitate, PbI2, forms when these solutions are mixed:

Pb(NO3)2(aq) + KI(aq) → PbI2(s) + 2KNO3(aq)

2. The two products of the reaction are insoluble copper (II) hydroxide and soluble potassium iodide.

CuI2(aq) + 2 KOH(aq) → Cu(OH)2(s) + 2 KI(aq)

A chemical reaction is typically followed by physical signs that are readily detected, such as heat and light emission, precipitate formation, gas evolution, or a change of appearance.

The shape or form of the matter varies through a physical transition, but the sort of matter in the material does not. In a chemical shift, however, the type of matter shifts and at least one new material with new properties is created. There is no straight cut of the gap between physical and chemical transition.

The purpose of writing a balanced chemical equation is to explain the occurring reactants (starting material) and products (end results). The ratios in which they answer so that you can measure the amount of reactants you need and the amount of goods you can make.

A chemical equation is the symbolic representation in the form of symbols and formulas of a chemical reaction in which the reactant entities on the left-hand side and the product entities on the right-hand side are given.

A skeleton equation is when each product that takes part in the reaction is written with the chemical formulas describing the chemical reaction. Examples: The term equation: oxygen + methane. Dioxide with carbon + Vapour.

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