Which reaction type is an element booted out and replaced by an other element?
|
Depending on conditions or the relative amounts of the reactants, more than one product can be formed in a combination reaction. Show
Decomposition chemical reactionsDecomposition reactions are really the opposite of combination reactions. In decomposition reactions, a single compound breaks down into two or more simpler substances (elements and/or compounds).The decomposition of water into hydrogen and oxygen gases,  and the decomposition of hydrogen peroxide to form oxygen gas and water, are examples of decomposition reactions. Single displacement chemical reactionsIn single displacement reactions, a more active element displaces (kicks out) another less active element from a compound. For example, if you put a piece of zinc metal into a copper(II) sulfate solution, the zinc displaces the copper, as shown in this equation:The notation (aq) indicates that the compound is dissolved in water — in an aqueous solution. Because zinc replaces copper in this case, it’s said to be more active. If you place a piece of copper in a zinc sulfate solution, nothing will happen. The following table shows the activity series of some common metals. Notice that because zinc is more active in the table, it will replace copper, just as the preceding equation shows. The Activity Series of Some Common MetalsActivityMetalMost activeAlkali and alkaline earth metalsAlZnCrFeNiSnPbCuAgLeast ActiveAuDouble displacement chemical reactionsIn single displacement reactions, only one chemical species is displaced. In double displacement reactions, or metathesis reactions, two species (normally ions) are displaced. Most of the time, reactions of this type occur in a solution, and either an insoluble solid (precipitation reactions) or water (neutralization reactions) will be formed.Precipitation reactionsIf you mix a solution of potassium chloride and a solution of silver nitrate, a white insoluble solid is formed in the resulting solution. The formation of an insoluble solid in a solution is called precipitation.Here is the molecular equation for this double-displacement reaction: The white insoluble solid that’s formed is silver chloride. Neutralization reactionsThe other type of double-displacement reaction is the reaction between an acid and a base. This double-displacement reaction, called a neutralization reaction, forms water. Take a look at the mixing solutions of sulfuric acid (auto battery acid) and sodium hydroxide (lye).Here is the molecular equation for this reaction: Combustion chemical reactionsCombustion reactions occur when a compound, usually one containing carbon, combines with the oxygen gas in the air. This process is commonly called burning. Heat is the most-useful product of most combustion reactions.Here’s the equation that represents the burning of propane: Propane belongs to a class of compounds called hydrocarbons, compounds composed only of carbon and hydrogen. The product of this reaction is heat. Combustion reactions are also a type of redox reaction. Redox chemical reactionsRedox reactions, or reduction-oxidation reactions, are reactions in which electrons are exchanged:The preceding reactions are examples of other types of reactions (such as combination, combustion, and single-replacement reactions), but they’re all redox reactions. They all involve the transfer of electrons from one chemical species to another. Redox reactions are involved in combustion, rusting, photosynthesis, respiration, batteries, and more. \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)
Learning Objectives
Up until now, we have presented chemical reactions as a topic, but we have not discussed how the products of a chemical reaction can be predicted. Here we will begin our study of certain types of chemical reactions that allow us to predict what the products of the reaction will be. A single-replacement reaction is a chemical reaction in which one element is substituted for another element in a compound, generating a new element and a new compound as products. Presented below: \[\ce{2HCl(aq) + Zn(s) → ZnCl2(aq) + H2(g)}\nonumber \] is an example of a single-replacement reaction. The hydrogen atoms in \(\ce{HCl}\) are replaced by \(\ce{Zn}\) atoms, and in the process a new element—hydrogen—is formed. Another example of a single-replacement reaction is \[\ce{2NaCl(aq) + F2(g) → 2NaF(s) + Cl2(g)}\nonumber \] Here the negatively charged ion changes from chloride to fluoride. A typical characteristic of a single-replacement reaction is that there is one element as a reactant and another element as a product. Not all proposed single-replacement reactions will occur between two given reactants. This is most easily demonstrated with fluorine, chlorine, bromine, and iodine. Collectively, these elements are called the halogens and are in the next-to-last column on the periodic table (Figure \(\PageIndex{1}\)). The elements on top of the column will replace the elements below them on the periodic table, but not the other way around. Thus, the reaction represented by \[\ce{CaI2(s) + Cl2(g) → CaCl2(s) + I2(s)}\nonumber \] will occur; but the reaction \[\ce{CaF2(s) + Br2(ℓ) → CaBr2(s) + F2(g)}\nonumber \] will not, because bromine is below fluorine on the periodic table. This is just one of many ways the periodic table helps us to understand chemistry. Example \(\PageIndex{1}\)Will a single-replacement reaction occur? If so, identify the products.
Solution
Exercise \(\PageIndex{1}\)Will a single-replacement reaction occur? If so, identify the products. \[\ce{FeI2 + Cl2 → }\nonumber \] AnswerYes; FeCl2 and I2 Chemical reactivity trends are easy to predict when replacing anions in simple ionic compounds—simply use their relative positions on the periodic table. However, when replacing the cations, the trends are not as straightforward. This is partly because there are so many elements that can form cations; an element in one column on the periodic table may replace another element nearby, or it may not. A list called the activity series does the same thing the periodic table does for halogens: it lists the elements that will replace elements below them in single-replacement reactions. A simple activity series is shown below. Activity Series for Cation Replacement in Single-Replacement Reactions
Using the activity series is similar to using the positions of the halogens on the periodic table. An element on top will replace an element below it in compounds undergoing a single-replacement reaction. Elements will not replace elements above them in compounds. Example \(\PageIndex{2}\)Use the activity series to predict the products, if any, of each equation.
Solution
Exercise \(\PageIndex{2}\)Use the activity series to predict the products, if any, of this equation. \[\ce{AlPO4 + Mg → }\nonumber \] AnswerMg3(PO4)2 and Al A double-replacement reaction occurs when parts of two ionic compounds are exchanged, making two new compounds. A characteristic of a double-replacement equation is that there are two compounds as reactants and two different compounds as products. An example is \[\ce{CuCl2(aq) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2AgCl(s)}\nonumber \] There are two equivalent ways of considering a double-replacement equation: either the cations are swapped, or the anions are swapped. (You cannot swap both; you would end up with the same substances you started with.) Either perspective should allow you to predict the proper products, as long as you pair a cation with an anion, and not a cation with a cation or an anion with an anion. Example \(\PageIndex{3}\)Predict the products of this double-replacement equation: \[\ce{BaCl2 + Na2SO4 → }\nonumber \] Solution Thinking about the reaction as either switching the cations or switching the anions, we would expect the products to be BaSO4 and NaCl. Exercise \(\PageIndex{3}\)Predict the products of this double-replacement equation: \[\ce{KBr + AgNO3 → }\nonumber \] AnswerKNO3 and AgBr Predicting whether a double-replacement reaction occurs is somewhat more difficult than predicting a single-replacement reaction. However, there is one type of double-replacement reaction that we can predict: the precipitation reaction. A precipitation reaction occurs when two ionic compounds are dissolved in water and form a new ionic compound that does not dissolve; this new compound falls out of solution as a solid precipitate. The formation of a solid precipitate is the driving force that makes the reaction proceed. To judge whether double-replacement reactions will occur, we need to know what kinds of ionic compounds form precipitates. For this, we use solubility rules, which are general statements that predict which ionic compounds dissolve (are soluble) and which do not (are not soluble, or insoluble). Table \(\PageIndex{1}\) lists some general solubility rules. We need to consider each ionic compound (both the reactants and the possible products) in light of the solubility rules. If a compound is soluble, we use the (aq) label with it, indicating that it dissolves. If a compound is not soluble, we use the (s) label with it and assume that it will precipitate out of solution. If everything is soluble, then no reaction will be expected. Table \(\PageIndex{1}\): Some Useful Solubility Rules (soluble)These compounds generally dissolve in water (are soluble):Exceptions:All compounds of Li+, Na+, K+, Rb+, Cs+, and NH4+NoneAll compounds of NO3− and C2H3O2−NoneCompounds of Cl−, Br−, I−Ag+, Hg22+, Pb2+Compounds of SO42Hg22+, Pb2+, Sr2+, Ba2+Table \(\PageIndex{2}\): Some Useful Solubility Rules (insoluble)These compounds generally do not dissolve in water (are insoluble):Exceptions:Compounds of CO32− and PO43−Compounds of Li+, Na+, K+, Rb+, Cs+, and NH4+Compounds of OH−Compounds of Li+, Na+, K+, Rb+, Cs+, NH4+, Sr2+, and Ba2+For example, consider the possible double-replacement reaction between Na2SO4 and SrCl2. The solubility rules say that all ionic sodium compounds are soluble and all ionic chloride compounds are soluble, except for Ag+, Hg22+, and Pb2+, which are not being considered here. Therefore, Na2SO4 and SrCl2 are both soluble. The possible double-replacement reaction products are NaCl and SrSO4. Are these soluble? NaCl is (by the same rule we just quoted), but what about SrSO4? Compounds of the sulfate ion are generally soluble, but Sr2+ is an exception: we expect it to be insoluble—a precipitate. Therefore, we expect a reaction to occur, and the balanced chemical equation would be: \[\ce{Na2SO4(aq) + SrCl2(aq) → 2NaCl(aq) + SrSO4(s)}\nonumber \] You would expect to see a visual change corresponding to SrSO4 precipitating out of solution (Figure \(\PageIndex{2}\)). Example \(\PageIndex{4}\)Will a double-replacement reaction occur? If so, identify the products.
Solution
Exercise \(\PageIndex{4}\)\[\ce{Sr(NO3)2 + KCl → }\nonumber \] AnswerNo reaction; all possible products are soluble. Key Takeaways
This page titled 4.3: Types of Chemical Reactions - Single and Double Replacement Reactions is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Anonymous via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. Which reaction type is an element booted out and replaced by another element?A single replacement reaction, sometimes called a single displacement reaction, is a reaction in which one element is substituted for another element in a compound.
What reaction is when one element replaces another element in a compound?Sometimes, an element replaces another element that is a part of a compound. This type of reaction is called a single- displacement reaction.
What is the type of reaction where one substance is replaced with another?A single-displacement reaction, also known as single replacement reaction or exchange reaction, is a chemical reaction in which one element is replaced by another in a compound.
What is the reaction called in which an element molecule or ion is removed by another?A single displacement reaction which is also called as single replacement reaction is a kind of oxidation-reduction chemical reaction when an ion or element moves out of a compound, i.e., one element is replaced by the other in a compound.
|
