Double Displacement Reaction

What Is a Double Displacement Reaction?

Let’s imagine ourselves going to a dance and having a dance partner. Once we arrive, we interact with the other people, and we end up switching dance partners with another person. Now you end up with a new dance partner. The same kind of thing can be compared to what occurs in a double displacement reaction in chemistry.

A double displacement reaction, also known as a double replacement reaction or metathesis, is a type of chemical reaction where two compounds react, and the positive ions (cation) and the negative ions (anion) of the two reactants switch places, forming two new compounds or products. Here, you can see the general form of a double displacement reaction:

How to Complete a Double Displacement Reaction

Just like how dance partners can be switched, the products of a double displacement reaction are the result of the cations and anions of the reactants trading partners with each other. Now we’ll learn the steps to complete and predict the correct products for a double displacement reaction. Let’s start with a look at the chemical reaction between Na 2 S and HCl.

Step 1: Identify the Individual Ions from the Reactants and Their Charges

For the reactant Na 2 S , there is a cation (positive ion) and an anion (negative ion). Na is written first, so that means Na is the cation. S is written second, so S is the anion. Cations and anions have charges that are either positive or negative integers. A cation has a positive charge, and an anion has a negative charge.

S has no subscript, which is just the small numbers at the bottom right after each element. No subscripts mean that the subscripts are equal to one. This means that if we rewrite the compound Na 2, the subscript for S is 1. We can then reverse the subscripts and figure out the individual charges of Na and S. Na has a charge of +1, and S has a charge of -2, as shown here:

Now, let us take a look at the other reactant, HCl. The cation is H, and the anion is Cl. Like we did with Na 2 S , we reverse the subscripts to figure out the individual charges.

Step 2: Switch the Cations and Anions of the reactants

To predict the products, bring down the charges as shown in this illustration:

Originally, the pairs are Na-S and H-Cl. Now, the new partner of Na is Cl, and the new partner of H is S.

Step 3: Balance the Chemical Reaction

The reaction in this case is not balanced, because the number of Na and H atoms (in red) is not the same.

What we need to do next is to balance the reaction by adding coefficients, which are the numbers before each compound. In this case, we will put a 2 in front of HCl to balance the H atoms and a 2 in front of NaCl to balance the Cl atoms.

Now, we have successfully balanced the reaction.

Examples of Double Displacement Reactions

For our first example, we’ll look at the reaction between Li 2 SO 4 and BaCl2 . SO4 is a polyatomic ion, so we will treat this as one anion. The ion SO4 does not have a subscript (4 is not the subscript because this is included in the ion). The subscript of SO4 is 1. Let’s first determine the ions and their charges.

Now, we can switch the ions and come up with the double displacement reaction.

For our next example, let’s look at the reaction between NaOH and CaBr2 . For this reaction, OH is a polyatomic ion and is treated as one whole anion. The individual ions and the charges for these two reactants are demonstrated in this image:

Now, we can switch the ions, as you can see here:

Types of Double Displacement Reactions

Now that we have gone over the steps to complete and balance double displacement reactions, let us go over the different types of double displacement reactions. There are three types of double displacement reactions: precipitation, neutralization and gas formation. We will discuss each and go over an example for each.

Precipitation Reaction

A precipitation reaction is when two compounds react and form a precipitate, which is a solid product. This product is insoluble, or cannot be dissolved in water.

For example, we have the reaction between NaCl and AgNO3 . When the two solutions, NaCl and AgNO3 , are mixed, a precipitate, AgCl, is formed. The subscript aq means aqueous, which means it is a solution in a solvent. The subscript s means solid. These subscripts indicate the phase of the compounds.

Going over the steps we outlined earlier to complete this double displacement reaction, we obtain the final reaction at the bottom of this image. The precipitate formed is AgCl, as indicated by the subscript s. The resulting reaction is already balanced, so there is no need to add coefficients.

Single-Displacement Reaction

What Is a Single-Displacement Reaction?

Imagine replacing something that you own – a car, a battery or a cell phone. We typically replace these objects with something similar, but better, like the latest model of your phone. We replace our possessions because the replacements will better suit our purposes, or because they will serve us better in the future. This is comparable to single-displacement reactions in chemistry.

A single-displacement reaction, also known as a single-replacement reaction, is a type of chemical reaction where an element reacts with a compound and takes the place of another element in that compound. This type of reaction is typically pictured like this:

Activity Series of Metal and Nonmetals

Just like we said earlier, we usually replace something if the replacement is better or will suit our purposes better. The replacement is usually similar to the original object. In the same way, for a single-displacement reaction, an element can only be replaced if the element taking its place is more reactive. For single-displacement reactions, a metal replaces a metal, and a nonmetal replaces a nonmetal. In the periodic table, we can see where the metals and the nonmetals are located. The metals are located on the left side of the stairs and the nonmetals are located on the right side of the stairs.

How do we know which element can replace another? We refer to the activity series. This tells us the reactivity of metals and nonmetals. A more reactive metal replaces a less reactive metal. A more reactive nonmetal replaces a less reactive nonmetal.

If we look at the activity series of metals, we see that H is included, even though H is not a metal. This is because, for single-displacement reactions, H usually behaves like a metal in chemical reactions. In the activity series of metals, we can say that Li can replace K in a single-displacement reaction because Li is more reactive than K. The same can be said for nonmetals: F can replace Br in a single-displacement reaction because F is more reactive than Br. Br has relatively the same reactivity as O.

For example, in this reaction, Cu replaces Ag because Cu is more reactive than Ag. We can confirm that by looking at the activity series of metals.

It is always important to predict the products of the chemical reaction correctly and make sure that the final chemical equation is balanced. In this reaction, it shows how we balanced the chemical equation. We put a coefficient 2 in front of AgNO3 and Ag to balance the number of Ag atoms and NO3 atoms on both sides.

Now, in this chemical reaction, a more reactive nonmetal replaces a less reactive nonmetal. In this case, Cl replaces Br because Cl is a more reactive nonmetal.

We need to take note that when Cl replaced Br, Br has a subscript of 2 in the products side. This is because Cl and Br are both in the same group in the periodic table, so we know they behave similarly.

How to Complete a Single-Displacement Reaction

To complete a single-displacement reaction, we have to go through a few steps to make sure that our products and our final reaction are correct.

Step one: Determine if the reaction will occur.

The reaction will only proceed if the element that replaces the original element is more reactive. For this reaction, the question is, can Zn replace H? We need to refer to the activity series. This tells us that Zn can replace H, so this reaction will occur.

Step two: Determine the products.

When H is replaced by Zn, H will naturally occur as H2, so on the products side, one of the products is H2. Zinc, a metal, will combine with Cl, a nonmetal. Since Zn is in the second group on the periodic table, it will have a charge of +2. Since Cl is in the halogen group on the periodic table, we know it has a charge of -1.

We need to combine Zn and Cl atoms such that the sum of their charges is equal to zero. In this case, there will be 1 zinc atom and 2 chlorine atoms. Our products will then be ZnCl2 and H2.

Step three: Balance the chemical reaction.

In this reaction, the number of H atoms and Cl atoms are not balanced, so we need to balance them by putting coefficients in front of the reactants and products, as needed.

 

BLOG#5: Decomposition Reaction

Decomposition Reaction Defined

A chemical reaction is a process by which the atoms of one or more substances are rearranged to form different substances. There are many types of chemical reactions. These reactions are often classified by what they form or what happens during the course of the reaction.

A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more elements or new compounds. These reactions often involve an energy source such as heat, light, or electricity that breaks apart the bonds of compounds.

For example:  The digestion of food in our body is accompanied by a number of decomposition reactions. The major constituents of our food such as carbohydrates, fats, proteins, etc.,decompose to form a number of simpler substances.  These substances further react, releasing large amounts of energy, which keeps our body working.

The general equation that describes a decomposition reaction is:

Types of Decomposition Reactions

Decomposition reactions can be classified into three types:

• Thermal decomposition reaction
• Electrolytic decomposition reaction
• Photo decomposition reaction

BLOG#4: Types of chemical reaction

Chemical reaction, a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are eitherchemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

Some examples of chemical reactions:

Example :1

Calcium + Hydrochloric →→ Calcium + Water + Carbon
Carbonate acid Chloride dioxide
CaCO₃ + HCl →→ CaCl₂ + H₂O + CO₂

In the above reaction, the balanced equation would be,

CaCO₃ + 2HCl →→ CaCl₂ + H₂O + CO₂

Calcium carbonate combines with hydrochloric acid to form three new products.

Example : 2

NaCl + AgNO₃ → AgCl + NaNO₃

This reaction is a double displacement reaction, where sodium and silver ions exchange the anions between them.

Example : 3

2Na +S → Na₂S
Sodium combines with sulfur to form sodium sulfide. This is a simple combination or a synthesis reaction, where two elements, sodium and sulfur combines to form sodium sulfide.

Example : 4

CaCO₃ → CaO + CO₂

Calcium carbonate decomposes in the above reaction to give two new products, calcium oxide and carbon dioxide. The carbon dioxide is a gas. It is usually denoted with an upward arrow, to show that it has escaped out.(↑)

Example : 5

CO₂ +H₂→ CO + H₂O
This reaction, though a combination reaction to give two new products, is also called a disproportionation reaction. A reaction, where two compounds combine and form two new compounds is called a disproportionation reaction.

Let’s start with the idea of a chemical reaction.Reactions occur when two or more molecules interact and the molecules change. Bonds between atoms are broken and created to form new molecules

BLOG #3: Rules in naming covalent compounds

However, simple covalent compounds are generally named by using prefixes to indicate how many atoms of each element are shown in the formula. Also, the ending of the last (most negative) element is changed to -ide. The prefixes used are mono-, di-, tri-, tetra-, penta-, hexa-, and so forth.