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Types of chemical reactions

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Intros
Lessons
  1. Spotting chemical patterns
  2. Why and how we categorize reactions.
  3. Reaction type: Neutralisation.
  4. Reaction type: Combustion
  5. Reaction type: Decomposition.
  6. Reaction type: Displacement
  7. Reaction type: Metathesis.
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Examples
Lessons
  1. Recall the main types of chemical reactions and how to identify them.
    Four reactions are shown below:
    Reaction 1: C5_5H12  (l)+_{12\;(l)} + 8 O2  (g)_{2\;(g)} →5 CO2  (g)+_{2 \;(g)} + 6 H2_2O  (g)_{\;(g)}
    Reaction 2: ZnSO4  (aq)+_{4\;(aq)} + Mg  (s)_{\;(s)} →MgSO4  (aq)+_{4\;(aq)} + Zn  (s)_{\;(s)}
    Reaction 3: CaCO3  (s)_{3\;(s)} →CaO  (s)+_{\;(s)} + CO2  (g)_{2\;(g)}
    Reaction 4: AgNO3  (aq)+_{3\;(aq)} + NaCl  (aq)_{\;(aq)} →AgCl  (s)+_{\;(s)} + NaNO3  (aq)_{3\;(aq)}
    1. Which of the reactions is a metathesis reaction? Explain how you know.
    2. Which of the reactions is a displacement reaction? Explain how you know.
    3. Which of the reactions is a decomposition reaction? Explain how you know.
  2. Balance equations and identify the type of reaction taking place.
    Balance and categorise the following equations:
    1. H2_2SO4+_4 + NaOH→Na2_2SO4+_4 + H2_2O
    2. Ca(NO3_3)2_2 →CaO+ + NO2+_2 + O2_2
    3. Cl2+_2 + NaBr→NaCl+ + Br2_2
  3. Apply knowledge of reaction types to predict products, balance equations and categorise the reaction.
    Complete and balance the reaction equations, then categorise them.
    1. BaCl2+_2 + Na2_2SO4_4 →
    2. NO2_2 →
    3. C6_6H14+_{14}+O2_2 →
    4. Ba(OH)2+_2 + H2_2SO4_4 →
Topic Notes
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Introduction

Chemical reactions are fundamental processes in chemistry where substances transform into new compounds. Understanding the types of chemical reactions is crucial for predicting outcomes and analyzing chemical processes. This lesson begins with an introductory video that provides a comprehensive overview of various chemical reactions, setting the foundation for deeper exploration. The video serves as a visual guide, illustrating key concepts and examples of different reaction types. Our objectives include analyzing chemical reactions in detail, comprehending their categorization based on specific characteristics, and developing the ability to predict reaction products. By mastering these skills, students will gain a solid understanding of how substances interact and change at the molecular level. This knowledge is essential for applications in diverse fields such as materials science, environmental studies, and pharmaceutical research. Throughout this lesson, we'll explore the fascinating world of chemical transformations and their significance in both laboratory settings and real-world scenarios.

Importance of Categorizing Chemical Reactions

Chemists categorize reactions for several important reasons, primarily to enhance prediction and efficiency in their work. Understanding the types of chemical reactions allows scientists to anticipate outcomes and streamline their research processes. This categorization is fundamental to grasping the patterns in chemical reactivity, which is essential for both theoretical understanding and practical applications in chemistry.

By organizing reactions into distinct categories such as synthesis, decomposition, single displacement, and double displacement, chemists can quickly identify similarities between different chemical processes. This classification system helps in predicting the products of a reaction, estimating reaction rates, and understanding the energy changes involved. For students and professionals alike, recognizing these patterns significantly reduces the amount of information that needs to be memorized, making chemistry more accessible and less daunting.

The concept of categorizing chemical reactions is closely related to the organization of the periodic table. Just as the periodic table's organization groups elements based on their properties and electron configurations, reaction categories group similar chemical processes. This systematic approach in both cases allows for predictions about chemical behavior. For instance, knowing an element's position in the periodic table can help predict its reactivity, just as understanding a reaction's category can help predict its outcome.

The periodic table's organization is a prime example of how categorization leads to predictive power in chemistry. Elements in the same group often exhibit similar chemical properties and reactivity patterns. This predictability extends to the types of reactions these elements are likely to undergo. For example, alkali metals in Group 1 are known for their high reactivity with water, while noble gases in Group 18 are typically unreactive due to their stable electron configurations.

By linking the categorization of reactions to the periodic table, chemists can make educated guesses about how elements will behave in various chemical scenarios. This connection between reaction types and elemental properties is a powerful tool in chemical research and industrial applications. It allows for more efficient experimental design, safer handling of chemicals, and more accurate predictions of reaction outcomes.

In conclusion, the categorization of chemical reactions is not just an academic exercise but a practical necessity in the field of chemistry. It enhances our understanding of chemical reactivity, improves predictive capabilities, and increases efficiency in both research and industrial settings. By relating this categorization to the periodic table, chemists create a comprehensive framework for understanding and predicting chemical behavior, making chemistry a more accessible and powerful science.

Neutralization Reactions

Neutralization reactions are a fundamental type of chemical reaction that occurs between an acid and a base. These reactions are essential in chemistry and have numerous applications in everyday life. In a neutralization reaction, an acid and a base combine to form water and a salt, effectively neutralizing each other's properties.

The general formula for a neutralization reaction can be expressed as:

Acid + Base Salt + Water

To understand neutralization reactions, it's crucial to identify acids and bases in chemical formulas. Acids are typically characterized by the presence of hydrogen (H) atoms that can be donated as protons. Common examples include hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3). Bases, on the other hand, are substances that can accept protons and often contain hydroxide (OH) groups. Examples of bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH3).

When identifying acids and bases in chemical formulas, look for these key indicators:

  • Acids often begin with "H" (hydrogen) in their formula
  • Bases frequently end with "OH" (hydroxide) or contain "NH" (ammonia)

Let's explore some common acids and bases:

Common Acids:

  • Hydrochloric acid (HCl) - found in stomach acid
  • Sulfuric acid (H2SO4) - used in car batteries
  • Acetic acid (CH3COOH) - the main component of vinegar
  • Citric acid (C6H8O7) - found in citrus fruits

Common Bases:

  • Sodium hydroxide (NaOH) - used in soap production
  • Potassium hydroxide (KOH) - found in some cleaning products
  • Magnesium hydroxide (Mg(OH)2) - the active ingredient in milk of magnesia
  • Ammonia (NH3) - used in household cleaners

When an acid and a base react in a neutralization reaction, the products are always a salt and water. The salt formed depends on the specific acid and base involved in the reaction. For example:

HCl (hydrochloric acid) + NaOH (sodium hydroxide) NaCl (sodium chloride, table salt) + H2O (water)

In this reaction, the hydrochloric acid and sodium hydroxide neutralize each other, producing common table salt and water. The resulting solution is neutral, with a pH of 7.

Neutralization reactions play a crucial role in various fields, including:

  • Environmental science: Neutralizing acidic pollutants in water and soil
  • Medicine: Treating acid reflux with antacids
  • Agriculture: Adjusting soil pH for optimal plant growth
  • Industry: Waste treatment and product manufacturing

Understanding neutralization reactions is essential for students and professionals in chemistry and related fields. These reactions demonstrate the fundamental principles of acid-base chemistry and provide insights into how substances interact at the molecular level. By recognizing the characteristics of acids and bases and understanding the products of their reactions, we can better comprehend the chemical processes that occur in our environment and in various applications.

Combustion Reactions

Combustion reactions are a fundamental type of chemical reaction that play a crucial role in our daily lives and various industrial processes. These exothermic reactions involve the rapid oxidation of a fuel, typically a hydrocarbon, in the presence of oxygen. The general formula for a combustion reaction can be expressed as: Fuel + Oxygen Carbon Dioxide + Water + Energy This seemingly simple equation represents a complex process with significant implications for energy production, transportation, and environmental concerns. Combustion reactions are particularly important in internal combustion engines, which power most vehicles on the road today. In these engines, the controlled combustion of gasoline or diesel fuel provides the energy necessary to move pistons and ultimately propel the vehicle forward. The role of oxygen in combustion reactions cannot be overstated. Oxygen acts as the oxidizing agent, accepting electrons from the fuel molecules and facilitating the breakdown of chemical bonds. This process releases energy in the form of heat and light. In most cases, the oxygen for combustion comes from the air, which is approximately 21% oxygen by volume. Hydrocarbons, compounds composed of hydrogen and carbon atoms, are the most common fuels in combustion reactions. These include natural gas (primarily methane), gasoline (a mixture of various hydrocarbons), and propane. When hydrocarbons undergo complete combustion, they react with oxygen to produce carbon dioxide (CO2) and water (H2O) as the primary products. For example, the combustion of methane (CH4) can be represented by the following balanced equation: CH4 + 2O2 CO2 + 2H2O + Energy This reaction demonstrates the formation of carbon dioxide and water, which are the common products of complete combustion reactions. The energy released during this process is what makes combustion reactions so valuable for heat and power generation. Identifying combustion reactions is relatively straightforward when examining the reactants and products. Key indicators include: 1. The presence of a fuel (often a hydrocarbon) and oxygen as reactants. 2. The production of carbon dioxide and water as primary products. 3. The release of energy, often in the form of heat and light. It's important to note that not all combustion reactions are complete. Incomplete combustion occurs when there is insufficient oxygen available for the reaction. This can result in the formation of carbon monoxide (CO) instead of carbon dioxide, which is both less efficient in terms of energy release and potentially hazardous. Understanding combustion reactions is crucial for addressing environmental concerns related to greenhouse gas emissions and air pollution. The carbon dioxide produced by these reactions contributes to global warming, prompting research into cleaner energy sources and more efficient combustion processes. In conclusion, combustion reactions are a vital part of our energy infrastructure and daily lives. Their significance extends from powering our vehicles to heating our homes and generating electricity. By understanding the principles behind these reactions, we can work towards optimizing their efficiency and mitigating their environmental impact, paving the way for a more sustainable future.

Decomposition Reactions

Decomposition reactions are a fundamental type of chemical reaction where a single compound breaks down into two or more simpler substances. These reactions are characterized by their unique structure: one reactant yields multiple products. This process is the opposite of synthesis reactions, making decomposition reactions an essential concept in understanding chemical transformations.

The general formula for a decomposition reaction can be represented as: AB A + B, where AB is the original compound, and A and B are the resulting products. This simple representation belies the complexity and variety of decomposition reactions that occur in nature and in laboratory settings.

Several factors can trigger decomposition reactions, with heat and light being among the most common. Thermal decomposition occurs when a substance breaks down due to high temperatures. For example, calcium carbonate (limestone) decomposes into calcium oxide and carbon dioxide when heated: CaCO CaO + CO. This reaction is crucial in the production of lime for construction and agricultural purposes.

Light can also initiate decomposition, particularly in photosensitive compounds. A prime example is the decomposition of silver chloride when exposed to light: 2AgCl 2Ag + Cl. This reaction forms the basis of traditional photography, where light causes silver halides to break down, creating an image on film.

Identifying decomposition reactions in chemical equations is straightforward. Look for a single reactant on the left side of the arrow and multiple products on the right. For instance, in the electrolysis of water (2HO 2H + O), we see one compound (water) breaking down into two elements (hydrogen and oxygen).

Decomposition reactions play vital roles in various fields. In chemistry, they're used to produce simpler substances from complex ones. In biology, the breakdown of complex molecules like proteins and carbohydrates during digestion is a form of decomposition. In industry, these reactions are harnessed for processes like the production of oxygen from potassium chlorate (2KClO 2KCl + 3O).

Understanding decomposition reactions is crucial for students and professionals alike. They form a cornerstone of chemical knowledge, alongside other types of reactions like synthesis, single displacement, and double displacement. By mastering the concept of decomposition reactions, one gains insight into the fundamental ways matter can transform, opening doors to deeper understanding in chemistry, biology, and materials science.

Displacement Reactions

Displacement reactions, also known as single replacement reactions, are a fundamental type of chemical reaction where one element replaces another in a compound. These reactions are essential to understand in chemistry and play a significant role in various industrial and natural processes. The general form of a displacement reaction can be represented as A + BC AC + B, where element A displaces element B from the compound BC.

To identify displacement reactions, look for the exchange of atoms or groups between compounds. In these reactions, a more reactive element takes the place of a less reactive element in a compound. This exchange results in the formation of a new compound and the release of the displaced element. Displacement reactions can involve both metals and non-metals, each with its own characteristics.

Metal displacement reactions occur when a more reactive metal replaces a less reactive metal in a compound. For example, when zinc (Zn) is added to a solution of copper sulfate (CuSO4), the zinc displaces the copper, forming zinc sulfate (ZnSO4) and releasing copper metal. The reaction can be written as: Zn + CuSO4 ZnSO4 + Cu. This type of reaction is common in metallurgy and is used in the extraction of metals from their ores.

Non-metal displacement reactions involve the replacement of one non-metal by another in a compound. A classic example is the reaction between chlorine gas (Cl2) and sodium bromide (NaBr) solution. The more reactive chlorine displaces bromine from the compound: Cl2 + 2NaBr 2NaCl + Br2. These reactions are often used in the production of halogens and other non-metal elements.

The key difference between metal and non-metal displacement reactions lies in the nature of the elements involved and the products formed. Metal displacement typically results in the formation of a new metal salt and the precipitation of the displaced metal. Non-metal displacement often involves the formation of a new ionic compound and the release of the displaced non-metal as a molecular substance.

To predict whether a displacement reaction will occur, it's crucial to understand the reactivity series of elements. Elements higher in the reactivity series can displace those lower down. For instance, magnesium (Mg) can displace copper (Cu) from copper sulfate because magnesium is more reactive than copper: Mg + CuSO4 MgSO4 + Cu. However, the reverse reaction will not occur spontaneously.

Displacement reactions have numerous practical applications. In the purification of metals, more reactive metals are used to extract less reactive ones from their compounds. This principle is applied in the extraction of copper from its ore using iron. In water treatment, chlorine is used to displace bromine from bromide salts, helping to purify water. The automotive industry utilizes displacement reactions in the production of car batteries, where lead displaces hydrogen from sulfuric acid.

Understanding displacement reactions is crucial for students and professionals in chemistry, metallurgy, and environmental science. These reactions help explain natural phenomena, such as the formation of rust when iron is exposed to oxygen and moisture, and are fundamental to many industrial processes. By mastering the concept of displacement reactions, one can better comprehend the behavior of elements and predict the outcomes of various chemical processes.

Metathesis Reactions

Metathesis reactions, also known as double replacement reactions, are a fundamental type of chemical reaction where two compounds exchange parts to form two new compounds. The general form of a metathesis reaction is AB + CD AC + BD, where A and C are typically metal cations, while B and D are usually non-metal anions. This reaction type is distinct from single displacement reactions, where a more reactive element replaces a less reactive element in a compound.

In contrast to single displacement reactions, metathesis reactions involve the exchange of ions between two compounds, rather than the replacement of one element by another. For example, when silver nitrate (AgNO3) reacts with sodium chloride (NaCl), the result is silver chloride (AgCl) and sodium nitrate (NaNO3). This can be represented as: AgNO3 + NaCl AgCl + NaNO3.

Metathesis reactions can involve both metal and non-metal exchanges. A common example of a metal exchange is the reaction between copper(II) sulfate and iron: CuSO4 + Fe FeSO4 + Cu. For non-metal exchanges, consider the reaction between hydrochloric acid and sodium hydroxide: HCl + NaOH NaCl + H2O.

To identify metathesis reactions in chemical equations, look for the exchange of ions between two compounds. The reactants should be two different compounds, and the products should also be two different compounds. The cations and anions switch partners in the process. Another key indicator is the formation of a precipitate or the evolution of a gas, which often occurs in these reactions.

Understanding metathesis reactions is crucial in chemistry as they are common in various applications, from water treatment to the production of industrial chemicals. By recognizing the patterns of these reactions, students and professionals can better predict the outcomes of chemical processes and understand the behavior of ionic compounds in solution.

Conclusion

Understanding the various types of chemical reactions is crucial for predicting and explaining chemical behavior. We've explored key reaction types including synthesis, decomposition, single displacement, double displacement, and combustion. Each type plays a unique role in chemical processes, from forming new compounds to breaking down existing ones. Mastering these concepts is essential for success in chemistry and related fields. Chemical reactions are the foundation of countless applications in industries such as pharmaceuticals, materials science, and environmental studies. By grasping these fundamental reaction types, you're better equipped to analyze and interpret chemical phenomena in both laboratory and real-world settings. As you continue your chemistry journey, delve deeper into these reaction types and their mechanisms. Explore how they manifest in everyday life and cutting-edge research. Remember, chemistry is a dynamic field with endless possibilities for discovery. Keep experimenting, questioning, and learning to unlock the fascinating world of chemical reactions!

Spotting Chemical Patterns: Why and How We Categorize Reactions

Understanding the categorization of chemical reactions is crucial for predicting the outcomes of various chemical processes. This guide will walk you through the reasons and methods for categorizing chemical reactions, based on the provided content.

Step 1: Introduction to Chemical Reactions

In this section, we begin by understanding the basics of chemical reactions. Chemical reactions involve the transformation of reactants into products. By analyzing these reactions, we can gain insights into the nature of the reactants and the products formed. This foundational knowledge is essential for further categorization and prediction of chemical reactions.

Step 2: Importance of Categorizing Chemical Reactions

Categorizing chemical reactions is a common practice in chemistry, especially at higher levels. The primary reason for this categorization is to simplify the understanding and prediction of chemical processes. By identifying a reaction as a specific type, such as a combustion or neutralization reaction, chemists can predict the products and the behavior of the reactants involved. This categorization helps in managing the vast number of chemical reactions and compounds that exist.

Step 3: Predicting Reaction Products

One of the significant benefits of categorizing chemical reactions is the ability to predict the products of a reaction. For instance, if a reaction is known to always involve oxygen as a reactant, chemists can predict that one of the products will likely be an oxide. Similarly, if a reaction involves a metal in its elemental form, the products can be anticipated based on the known reactivity of metals. This predictive capability is invaluable in both academic and industrial chemistry.

Step 4: Spotting Patterns in Chemical Reactions

Spotting patterns in chemical reactions is a key aspect of categorization. By observing recurring themes and behaviors in reactions, chemists can group similar reactions together. This pattern recognition reduces the need for conducting numerous experiments, saving time and resources. For example, the periodic table itself is a tool for spotting patterns in chemical reactivity, with its arrangement reflecting the properties and behaviors of elements.

Step 5: Practical Applications of Categorization

The practical applications of categorizing chemical reactions are vast. In industrial settings, knowing the type of reaction can help in designing processes to manufacture desired products efficiently. In educational contexts, it aids in teaching and understanding complex chemical concepts. By categorizing reactions, chemists can also develop new reactions and compounds by extrapolating from known patterns and behaviors.

Step 6: Conclusion

In conclusion, categorizing chemical reactions is a fundamental practice in chemistry that offers numerous benefits. It allows for the prediction of reaction products, saves time and resources, and facilitates a deeper understanding of chemical processes. By recognizing and utilizing patterns in chemical reactivity, chemists can advance both theoretical knowledge and practical applications in the field of chemistry.

FAQs

  1. What are the 5 types of chemical reactions?

    The five main types of chemical reactions are:

    • Synthesis (Combination) reactions
    • Decomposition reactions
    • Single displacement reactions
    • Double displacement (Metathesis) reactions
    • Combustion reactions

    Each type has distinct characteristics and plays a unique role in chemical processes.

  2. What are some examples of chemical reactions in everyday life?

    Common examples include:

    • Rusting of iron (oxidation)
    • Burning of wood (combustion)
    • Cooking of food (various reactions)
    • Photosynthesis in plants
    • Battery operation (redox reactions)

  3. How can you identify a combustion reaction?

    Combustion reactions can be identified by:

    • The presence of a fuel and oxygen as reactants
    • Production of carbon dioxide and water as primary products
    • Release of heat and often light
    • Rapid oxidation of the fuel

  4. What is the difference between single and double displacement reactions?

    Single displacement reactions involve one element replacing another in a compound (A + BC AC + B). Double displacement reactions, also known as metathesis, involve two compounds exchanging parts to form two new compounds (AB + CD AC + BD).

  5. Why is understanding chemical reactions important?

    Understanding chemical reactions is crucial because:

    • It helps predict outcomes of chemical processes
    • It's essential for developing new materials and medicines
    • It aids in understanding environmental processes
    • It's fundamental to many industrial applications
    • It enhances problem-solving skills in chemistry and related fields

Prerequisite Topics for Understanding Types of Chemical Reactions

To fully grasp the concept of types of chemical reactions, it's crucial to have a solid foundation in several key areas of chemistry. One of the most fundamental prerequisites is an introduction to chemical reactions. This foundational knowledge helps students understand the basic principles of how substances interact and transform, setting the stage for more complex reaction classifications.

Another essential prerequisite is understanding state symbols and phase changes. This topic is particularly relevant when studying types of chemical reactions because many reactions involve changes in the physical state of substances. For instance, precipitation reactions result in the formation of a solid from aqueous solutions, while combustion reactions often involve gases. Familiarity with state symbols and phase changes allows students to better interpret and predict the outcomes of various reaction types.

The history and development of the periodic table might seem less directly related, but it's actually quite significant. The periodic table's organization reflects the chemical properties of elements, which in turn influences their reactivity and the types of reactions they undergo. Understanding how elements are arranged and why can provide valuable insights into predicting reaction types and products.

Lastly, knowledge of conjugate acids and bases is crucial for comprehending acid-base reactions, which are a major category of chemical reactions. This prerequisite topic helps students identify acids and bases in reactions, understand proton transfer, and predict the products of neutralization reactions.

By mastering these prerequisite topics, students build a strong conceptual framework that enables them to tackle the complexities of various chemical reaction types. The ability to recognize and classify reactions is not just about memorizing categories; it requires a deep understanding of chemical behavior, which is rooted in these fundamental concepts.

For example, when studying synthesis reactions, students draw upon their knowledge of chemical equations and the periodic table to predict how elements combine. In decomposition reactions, understanding phase changes becomes crucial as substances often break down into simpler components in different states. Redox reactions, which involve electron transfer, are better understood with a solid grasp of periodic trends and elemental properties.

Moreover, these prerequisite topics don't just facilitate learning about reaction types; they also enhance problem-solving skills in chemistry. When faced with complex reaction scenarios, students can apply their knowledge of basic principles to analyze and predict outcomes, making the study of chemical reactions more intuitive and less about rote memorization.

In conclusion, the journey to mastering types of chemical reactions is built upon a foundation of these interconnected prerequisite topics. By investing time in understanding these fundamental concepts, students set themselves up for success in more advanced chemistry studies and develop a more holistic view of chemical processes.

In this lesson, we will learn:
  • To analyze chemical reactions in terms of the reactants and products involved.
  • To understand the value of categorizing reactions in chemistry.
  • To predict the products of chemical reactions based on the reactants involved.

Notes:
  • A lot of chemical reactions can be categorized by the reactants they use or the products they form. There are many types including neutralization, combustion, displacement, decomposition and metathesis. This is useful to predict the requirements and outcomes of a reaction you're doing!

  • Neutralization reactions are identified by the use of an acid and an alkali.
    • An acid can normally be spotted by the formula beginning with H (such as HCl, H2SO4 or HNO3).
    • An alkali can likewise normally be spotted by the formula ending in OH as a group (such as NaOH, Ca(OH)2 etc)
    • Neutralization reactions produce water and a salt, made of the metal ion(s) of the alkali and the negative ion(s) of the acid involved. These are the remaining compound fragments that did not form water.
    • An example of a neutralization reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is below:

      • HCl ++ NaOH  \, →  \, NaCl ++ H2O

  • Combustion reactions are defined by the use of oxygen gas to react with one other chemical.
    • Combustion of hydrocarbons is a very common reaction, and is how most cars generate power.
    • Combustion is technically any reaction with oxygen. Some good evidence for a combustion reaction is a compound of oxygen in the products that wasn't in the reactants.
    • You can think of combustion as a chemical name for 'burning' – it is technically any reaction with oxygen.
    • An example of a combustion reaction with pentane, C5_5H12_{12}, is below:

      • C5H12 ++ 8O2  \, →  \, 5CO2 ++ 6H2O

  • Displacement reactions involve an atom or groups of atoms being exchanged or 'swapped' from a chemical compound.
    • Displacement reactions involve a metal (or non-metal) in elemental form e.g. Mg (or Cl2_2) and a metal (or non-metal) in a salt (e.g. ZnBr2_2) where the two metals (or non-metals) exchange.
    • An example of a displacement between two non metals (chlorine and bromine) is below:

      • Cl2 ++ MgBr2  \, →  \, MgCl2 ++ Br2

  • Metathesis reactions involve atoms or groups of atoms being exchanged between two different chemical compounds containing both metal and non-metal ions.
    • Metathesis is similar to a displacement reaction except two compounds are displaced, not one. For this reason metathesis reactions are sometimes called double displacements.
    • An example of a metathesis reaction is below:

      • BaCl2 ++ 2 AgNO3  \, →  \, Ba(NO3)2 ++ 2 AgCl

  • Decomposition reactions involve one chemical compound reactant breaking down into two or more products which were originally part of the starting material.
    • Decomposition reactions are easy to spot – they normally only have one reactant which is the compound that is decomposing!
    • An example of a decomposition reaction is below:

      • 2H2O2  \, →  \, 2H2O ++ O2