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# Types of Chemical Reactions

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What does lighting a candle, digesting food, washing your hands, and driving a car all have in common? They are all types of chemical reactions in our daily life.

A chemical reaction is a conversion of one or more elements/compounds (called reactants) into one or more elements/compounds (called products). We illustrate this reaction using a chemical equation.

There are several types of chemical reactions: each with its own unique characteristics. In this article, we'll go into detail about the different types of chemical reactions and how to identify them.

• The article is about the types of chemical reactions.
• We will learn about and see examples of the 4 main types of chemical reactions.
• We will see how to tell these types of reactions apart based on their characteristics.
• We will also learn how to write reactions based on their type.

## Different Types of Chemical Reactions

There are 4 types of chemical reactions: synthesis, decomposition, combustion, and replacement.

### Synthesis reactions

The first type of reaction we will cover is the synthesis reaction.

A synthesis reaction involves two elements/compounds combining to form a singular compound.

The general form of this reaction is:

$$X + Y \rightarrow XY$$

Synthesis reactions are also known as combination reactions, since species are "combining" to form a product. Here are some examples of synthesis reactions:

$$2Na + Cl_2 \rightarrow 2NaCl$$

$$2H_2 + O_2 \rightarrow 2H_2O$$

$$Li_2O + H_2O \rightarrow 2LiOH$$

The key characteristic of a synthesis reaction is that there is always only one product.

### Decomposition Reactions

The second type of chemical reaction is called a decomposition reaction.

A decomposition reaction is a reaction where a compound splits into two or more elements or compounds.

The general form of this reaction is:

$$XY \rightarrow X + Y$$

Since decomposition reactions involve breaking bonds, they typically require energy to complete. Decomposition is the opposite of synthesis. Here are some examples of decomposition reactions

$$2Al_2O_3 \rightarrow 4Al + 3O_2$$

$$Ca(OH)_2 \rightarrow CaO + H_2O$$

$$H_2SO_3 \rightarrow H_2O + SO_2$$

The key characteristic of a decomposition reaction is that you start with one reactant and end with 2 or more products.

### Combustion Reactions

The third type of chemical reaction is a combustion reaction.

A combustion reaction occurs when a compound or element reacts with oxygen gas to release energy (typically in the form of fire). These reactions usually involve a hydrocarbon, which is a compound that contains only C and H.

The general reaction for a hydrocarbon combustion reaction is:

$$C_xH_y + O_2 \rightarrow aCO_2 + bH_2O$$

The products of a combustion reaction are in the gaseous state, since these reactions are very hot. Since the combustion of these can release a lot of heat energy, hydrocarbons are often used as fuel. Butane, for example, is used in lighters. Here are some other examples of combustion reactions:

$$2C_6H_{14} + 19O_2 \rightarrow 12CO_2 + 14H_2O$$

$$2CH_3OH + 3O_2 \rightarrow 2CO_2 + 4H_2O$$

$$2H_2 + O_2 \rightarrow 2H_2O (Note: this is the combustion of hydrogen gas which produces water vapor, not the synthesis of liquid water. However, this is still also a synthesis reaction!) The key component of these reactions is oxygen gas. It wouldn't be a combustion reaction without it! ### Replacement reactions (single and double) The fourth type of chemical reaction is the replacement reaction. A replacement reaction involves the swapping of one or more elements between compounds. A single replacement reaction is the swapping of only one element, while a double replacement reaction is the swapping of two elements. The general formula for these reactions are (in order):$$X + YZ \rightarrow XY + ZXY + ZA \rightarrow XA + ZY$$Note: The order of elements will stay the same when swapped, if "X" is the first element in "XY" then it will also be the first element in "XA" Single replacement reactions typically involve the swapping of metals. The lone metal kicks out the other metal because it is more reactive. We use a reactivity series to see if one metal can replace another. A reactivity series is a chart that ranks metals based on their reactivity. If a metal is less reactive, then it cannot swap with the metal in the compound. For double replacement reactions, the cations (positively charged ions) are the ones that swap. They typically occur in an aqueous solution (solids have been dissolved in water). Below are some examples of both types of replacement reactions.$$Zn + 2HCl \rightarrow ZnCl_2 + H_2ZnCl_2 + MgSO_4 \rightarrow ZnSO_4 + MgCl_2Li + MgCl_2 \rightarrow LiCl_2 + Mg2KI + Pb(NO_3)_2 \rightarrow 2KNO_3 + PbI_2$$A special type of double replacement reaction is called a precipitate reaction. In this type of reaction, two aqueous solutions form a solid called a precipitate and another aqueous solution. We determine which product will be a solid based on solubility rules. When certain ions are combined, they can be either insoluble or soluble in water. Insoluble compounds form a precipitate. There are a lot of solubility rules, so chemists often use handy charts to help them remember them all! Here are some examples of a precipitate reaction:$$Pb(NO_3)_{2\,(aq)} + 2NaI_{(aq)} \rightarrow PbI_{2\,(s)} + 2NaNO_{3\,(aq)}Li_2CO_{3\,(aq)} + Ca(NO_3)_{2\,(aq)} + 2LiNO_{3\,(aq)} + CaCO_{3\,(s)}$$For precipitate reactions, only one of the products is a solid, the other will be aqueous. ## Types of chemical reactions chart Now that we have covered each of the 4 types of chemical reaction, we can identify the type of chemical reaction based on key characteristics. Here is a chart breaking down what we have learned so far: Types of Chemical Reactions Chart Type of ReactionCharacteristicsGeneral form(s)Example(s) SynthesisTwo or more species combine into one species$$X + Y \rightarrow XY2H_2 + O_2 \rightarrow 2H_2O$$DecompositionOne species breaks down into two or more species$$XY \rightarrow X + YCa(OH)_2 \rightarrow CaO + H_2O$$CombustionA species reacts with oxygen gas, which releases energy. Typically done with a hydrocarbon (CH compound)$$C_xH_y + O_2 \rightarrow aCO_2 + bH_2O$$(for hydrocarbons only)$$2CH_3OH + 3O_2 \rightarrow 2CO_2 + 4H_2O$$ReplacementSingle: One element swaps with another element of a different compoundDouble: An element from each compound swaps between them$$X + YZ \rightarrow XZ + Y\,\text{(Single)}XY + ZA \rightarrow XA + ZY\,\text{(Double)}Li + MgCl_2 \rightarrow LiCl_2 +Mg\,\text{(Single)}2KI + Pb(NO_3)_2 \rightarrow 2KNO_3 + PbI_2\,\text{(Double)}$$## Identify the type of chemical reaction Let's look at some equations and see if we can determine their type. Another important thing to note is that some reactions have an overlap. A previous example is the combustion of hydrogen gas, which is also a synthesis reaction.$$2KClO_3 \rightarrow 2KCl + 3O_2$$Since a molecule is being broken down, this is a decomposition reaction$$2Mg + O_2 \rightarrow 2MgO$$This reaction is both a synthesis (because two species are being combined) and a combustion reaction (because oxygen gas is involved)$$AgNO_3 + NaCl \rightarrow AgCl + NaNO_3$$Since two species are being swapped (Ag and Na), then this is a double replacement reaction ## Types of chemical reactions in our daily life All the way back in the intro, we talked about different reactions in our daily life. Now that we've covered the types of chemical reactions, we can label these common reactions: • Lighting a candle is a combustion reaction, since striking a match causes a reaction that produces a flame. Driving a car involves several reactions, but it also involves combustion as gasoline is burned. • Digesting food is a set of complex reactions, but is overall a decomposition reaction, as the food we eat is broken down by our stomach acids. • Lastly, washing your hands is also a complex decomposition reaction. The soap has two "ends": hydrophobic (water-hating) and hydrophilic (water-loving) end. The dirt on our hands is "attacked" by the hydrophobic end. The broken-down particles are released and go towards the hydrophilic end. This is then washed down the drain with the water. ## Writing different types of chemical Reactions Now that we have covered the characteristics of different chemical reactions, we can begin to learn how to write chemical reactions. There are 4 main steps to writing a chemical reaction: 1. Determine the type of reaction. 2. Determine the reactants and products. 3. Write the basic equation. 4. Balance the equation. Let's start with an example: Draw the reaction of nickel (III) oxide breaking down: 1. First, we need to determine the type of reaction. The key phrase here is "breaking down", which means we have a decomposition reaction. Next, we need to figure out our key players. 2. The number next to nickel, in the name "nickel (III) oxide", refers to its charge; this means that nickel is +3. Oxide (O2-) is the anion of oxygen, which has a charge of -2, so our reactant is Ni2O3. 3. In a decomposition reaction, the compound splits into 2 or more simpler substances that are more stable than the reactant. So, our compound would break down into Ni metal and O2 (O3 is very reactive/unstable, while O2 is less so). Here is our basic equation:$$Ni_2O_3 \rightarrow Ni + O_2$$4. Now for our last step, we need to balance this equation. We have 2 mols of Ni and 3 mols of O on the left, while there is 1 mol and 2 mols of O on the right. We must have an even amount of O on both sides, so we first multiply Ni2O3 by 2 to get:$$2Ni_2O_3 \rightarrow Ni + O_2$$Now we have on our left 4 mols of Ni and 6 mols of O. To finish balancing, we can multiply Ni by 4 and O2 by 3 to get:$$2Ni_2O_3 \rightarrow 4Ni + 3O_2

It's important to look at the wording of a problem, since it can help you figure out what kind of reaction is happening. Phrases like "forms" and "creates" likely mean a synthesis reaction is happening, while phrases like "burning" and "explosion" mean a combustion reaction is happening. Replacement reactions don't really have such phrases, so if there is no clear phrasing, then it's probably a replacement reaction!

## Types of Chemical Reactions - Key takeaways

• There are 4 types of chemical reactions: synthesis, decomposition, combustion, and replacement
• A synthesis reaction involves two elements/compounds combining to form a singular compound.
• A decomposition reaction is a reaction where a compound splits into two or more elements or compounds.
• A combustion reaction occurs when a compound or element reacts with oxygen gas to release energy (typically in the form of fire). These reactions typically involve a hydrocarbon, which is a compound that contains C and H.
• A replacement reaction involves the swapping of one or more elements between compounds. A single replacement reaction is the swapping of only one element, while a double replacement reaction is the swapping of two elements.
• A special type of double replacement reaction is called a precipitate reaction. In this type of reaction, two aqueous solutions (solids dissolved in water), form a solid, called a precipitate, and another aqueous solution.
• By understanding the different types of reactions, we can write chemical equations when given a description of the reaction.

The four types of chemical reactions are synthesis, decomposition, combustion, and replacement reactions.

The chemical equation for photosynthesis is actually a summary of several reactions. In general, the reaction is a synthesis reaction.

Both combustion and double replacement reactions occur in fireworks. The initial explosion of fireworks is a combustion reaction. The reaction that creates the various colors of light is a double replacement reaction. Depending on the type of metal swapped, different colors are produced.

Terms like "creates" and "forms" mean a reaction is a synthesis reaction. Terms like "breaks down" and "splits" mean a reaction is a decomposition reaction. Lastly, terms like "explosion" and "ignition" mean is reaction is a combustion reaction.

A) Combustion, Synthesis, Dissolvation

B) Decomposition, Replacement, Solidification

C) Combustion, Replacement, Synthesis

The answer is C. Dissolvation and Solidification are not types of chemical reactions.

## Types of Chemical Reactions Quiz - Teste dein Wissen

Question

What is a precipitate reaction?

A special type of double replacement reaction where two aqueous compounds form a solid

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Question

What must be true about a metal if it can participate in a single replacement reaction?

It is more reactive than the metal in the compound

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Question

True or False: Synthesis reactions produce one or more products

False

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Question

What are the products in the reaction of K2SO4 and Ba(NO3)2?

KNO3 and BaSO4

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Question

What is a redox reaction?

redox reaction involves the transfer of electrons from one species to another. In a redox reaction, the oxidation state of two species changes, with one being reduced (decreased) and one being oxidized (increased).

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Question

What is the oxidation number of the anion and cation in these compounds?

NaH, Co(OH)2, and VO2

NaH: Na(+1), H(-1)

Co(OH)2: Co(+2), OH(-1)

VO2: V(+4), O(-2)

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Question

True or False: Photosynthesis is the work of 2 redox reactions

True

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Question

What is the oxidation number of Cl is KClO3?

+5

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Question

What is the difference between an oxidizing agent and a reducing agent?

The species that is accepting the electrons is the oxidizing agent, while the species that is donating the electrons is the reducing agent

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Question

What is an oxidation state?

The oxidation state (also called oxidation number) corresponds to the number of electrons a species will give or receive during bonding.

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Question

What are the steps in the half-reaction method of balancing? (not including those related to acidic and basic conditions)

1. Write the unbalanced reaction in its ionic form
2. Determine the oxidation state of every species in the reaction
3. Determine which species is being oxidized, and which is being reduced
4. Split the reaction into the two half-reactions
5. Use electrons to balance the charge for each half-reaction.
6. Multiply the necessary half-reactions so that the number of electrons cancels
7. Combine each half-reaction and cancel like terms

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Question

What are the special steps taken when using the half-reaction method in acidic and basic solutions?

For acidic solutions: Use H2O to balance oxygen atoms and use Hto balance hydrogen atoms.

For basic solutions: Use H2O to balance oxygen atoms and use Hto balance hydrogen atoms. After the two half-reactions are combined, add OH- to neutralize any H+ atoms and convert them into H2O molecules.

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Question

What is a Brønsted-Lowry acid-base reaction?

A Brønsted-Lowry acid is a species that can donate a proton (H+ ion) while a Brønsted-Lowry base is a species that will accept that proton.

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Question

What does it mean when a species is amphoteric?

The species can act as an acid and a base

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Question

What is a polyprotic acid?

A polyprotic acid is a Brønsted-Lowry  acid that can donate multiple protons

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Question

What is a neutralization reaction?

In a neutralization reaction, a Brønsted-Lowry acid and base react to form a neutral salt and water.

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Question

What is a Lewis acid-base reaction?

Lewis acid-base reaction is between a Lewis acid and Lewis base. A Lewis acid (also called an electrophile) accepts electrons from a Lewis base (also called a nucleophile). An electrophile "loves electrons" and has an empty orbital for a lone pair from the nucleophile. The nucleophile "attacks" the positively charged electrophile and gives it that extra lone pair

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Question

What is a coordination complex?

coordination complex is a complex with a metal ion in the center and other smaller ions bonded to it. A Lewis base is typically the ligand (things attached to the metal), while the metal acts a Lewis acid. A complex ion is a coordination complex that has a charge.

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Question

True or False: The lone pair of electrons in a Lewis acid reside in its highest occupied molecular orbital (HOMO).

False

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Question

Why doesn't the Bronsted-Lowry concept of acids and bases explain how complex ions are formed?

The formations of these ions don't involve the movement of protons

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Question

True or False: NaOH is amphoteric

False

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Question

Which of the following is a characteristic of an electrophile?

Can have a polarizable double-bond

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Question

What type of acid-base reaction is baking soda (NaHCO3) and vinegar (HC2H3O2)?

Brønsted-Lowry

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