Understanding Chemical Reactions: Synthesis and Decomposition, Slides of Chemistry

Download Understanding Chemical Reactions: Synthesis and Decomposition and more Slides Chemistry in PDF only on Docsity! Types of Chemical Reactions: Synthesis & Decomposition Reactions Click on this icon for audio There are millions of chemical reactions that are known to occur. Among these millions of reactions, certain types display similar characteristics. As a result, chemists are able to group reactions into 4 basic types to help organize these known reactions and to help chemists predict the products of unknown reactions. Click to learn about synthesis reactions Synthesis Decomposition Single Displacement Double Displacement Click on this icon for audio A good example of a synthesis reaction occurs when diatomic molecules of hydrogen gas (H2 (g)) burn in the air, combining with diatomic molecules of oxygen gas (O2 (g)) to form water. Try to write out the balanced chemical equation for this reaction and you will see the general formula for a synthesis reaction represented. Balanced Synthesis Reaction Equation Click on this icon for audioSynthesis Reactions A good example of a synthesis reaction occurs when diatomic molecules of hydrogen gas burn in the air, combining with diatomic molecules of oxygen gas to form water. 2H2 (g) + O2 (g)  2H2O (l) Test Your Understanding As you can see from the reaction equation, the two reactant molecules combine to form one more complex molecule. The animation below represents this synthesis reaction occurring, as hydrogen and oxygen molecules react to form water molecules. Click on this icon for audioSynthesis Reactions Test your understanding: Which of the following reactions is a synthesis reaction? (Click the box with the correct answer.) 2HCl H2 + Cl22Fe + 6NaBr 2FeBr3 + 6 Na C2H8 + O2  2CO2 + 4H2OCO2 + H2O  H2CO3 Synthesis Reactions Decomposition Reactions In a decomposition reaction, one large reactant compound breaks down (or decomposes) into two or more smaller substances. A decomposition reaction is the opposite of a synthesis reaction. Using this information, try to write a general formula for a decomposition reaction before clicking the button below. Click for the General Formula for a Decomposition Reaction Click on this icon for audio In a decomposition reaction, one large reactant compound breaks down (or decomposes) into two or more smaller substances. The general formula for a decomposition reaction can be written as follows: Where the compound AB is the reactant which decomposes into the products A and B. More on Decomposition Reactions Decomposition Reactions Click on this icon for audio Reactants in a decomposition reaction can decompose into simple elements, more complex compounds or combinations of the two. For example, simple ionic compounds often decompose into their more simple elemental forms. Potassium chloride (KCl) decomposes into solid potassium (K) and chloride gas (Cl2) when electricity is used to provide energy. Write the balanced reaction equation for this reaction. Decomposition of KCl Decomposition Reactions Click on this icon for audio A good example of a decomposition reaction is commonly referred to as the pharaoh’s serpent reaction in which a white powder made up of mercury thiocyanate is ignited resulting in a visually stunning decomposition reaction. Click to view the Pharaoh’s Serpent Reaction Decomposition Reactions Click on this icon for audio A good example of a decomposition reaction is commonly referred to as the pharaoh’s serpent reaction in which a white powder made up of mercury thiocyanate is ignited resulting in a visually stunning decomposition reaction. Click for the Reaction Equation Decomposition Reactions Click on this icon for audio In the pharaoh’s serpent reaction the large, complex molecule mercury thiocyanate, (Hg(SCN)2 ) decomposes into carbon nitride (C3N4), mercury sulfide (HgS) and carbon disulfide (CS2) when energy is provided in the form of a flame or spark. Try to write the balanced equation for this reaction on your own, then click the button below to view it. Pharaoh’s Serpent Reaction Equation Decomposition Reactions Click on this icon for audio Which of the following reactions is a decomposition reaction? (Click the box with the correct answer.) 2HCl H2 + Cl22Al + 3Br2  2AlBr2 CaO + H2O Ca(OH)2P4 + 5O2  2P2O5 Incorrect. Try again: Decomposition Reactions Correct In the reaction: 2HCl H2 + Cl2 One reactant breaks down into 2 smaller substances, indicating a decomposition reaction has taken place. Success Criteria Decomposition Reactions Click on this icon for audio Success! You have reached the end of this activity. You will know that you have achieved the goals for this activity when you can describe and identify synthesis and decomposition reactions and can give examples of different types of these reactions. Back to Start