Metals single-displacement reactions

The electrons that are being lost by the zinc metal are the same electrons that are being gained by the copper(II) ion. The zinc metal is being oxidized and the copper(II) ion is being reduced. Further discussions on why reactions such as these occur can be found in the section on single-displacement reactions later in this chapter. 

In your previous chemistry course, you compared the reactivities of metals. You may recall that, when a piece of zinc is placed in an aqueous solution of copper(II) sulfate, the zinc displaces the copper in a single displacement reaction. This reaction is shown in Figure 10.1. As the zinc dissolves, the zinc strip gets smaller. A dark red-brown layer of solid copper forms on the zinc strip, and some copper is deposited on the bottom of the beaker. The blue colour of the solution fades, as blue copper(ll) ions are replaced by colourless zinc ions. 

You already know that some metals are more reactive than others. You may also have carried out an investigation on the metal activity series in a previous course. In Investigation 10-A, located on page 470, you will discover how this series is related to oxidation and reduction. You will write chemical equations, ionic equations, and half-reactions for the single displacement reactions of several metals. 

Magnesium exhibits single displacement reactions, thus replacing lower metals in electrochemical series from their salt solutions or melt. For example, magnesium will replace iron from molten iron(II) chloride forming magnesium chloride ... 

Many metals, such as zinc, iron, lead, copper, and aluminum are found chemically bonded to oxygen in nature. Sometimes, chemists can use single displacement reactions to get the pure metal. 

In a single displacement reaction, one element in a compound is displaced (or replaced) by another element. Two general reactions represent two different types of single displacement reactions. One type involves a metal replacing a metal cation in a compound, as follows ... 

Single Displacement Reactions and the Metal Activity Series... 

Most single displacement reactions involve one metal displacing another metal from a compound. In the following equation, magnesium metal replaces the zinc in ZnCl2, thereby liberating zinc as the free metal. 

The following three reactions illustrate the various types of single displacement reactions involving metals ... 

Through experimentation, chemists have ranked the relative reactivity of the metals, including hydrogen (in acids and in water), in an activity series. The reactive metals, such as potassium, are at the top of the activity series. The unreactive metals, such as gold, are at the bottom. In Investigation 4-A, you will develop an activity series using single displacement reactions. 

How do you think an activity series for metal would help you predict whether or not a single displacement reaction will occur Use examples to help you explain your answer. 

A single displacement reaction always favours the production of the less reactive metal. In other words, the "free" metal that is formed from the compound must always be less reactive than the metal that displaced it. For example,... 

Non-metals, typically halogens, can also take part in single displacement reactions. For example, molecular chlorine can replace bromine from KBr, an ionic compound, producing bromine and potassium chloride. 

In the same way as you used the activity series for metals, you can use the activity series for halogens to predict whether substances will undergo a single displacement reaction. For example, fluorine is above chlorine in the activity series. So, given the reactants fluorine and sodium chloride, you can predict that the following reaction will occur ... 

Q O Copper can be recovered from scrap metal by adding sulfuric acid. Soluble copper sulfate is formed. The copper sulfate then reacts with metallic iron in a single displacement reaction. To simulate this reaction, a student places 1.942 g of iron wool in a beaker that contains 136.3 mL of 0.0750 mol/L aqueous copper(II) sulfate. What mass of copper is formed ... 

A single replacement reaction occurs when an element reacts with a compound in such a way that the element replaces an ion of a similar element from the compound. In order for the replacement to occur, the elemental reactant must be more reactive than the elemental product. The general format for a single displacement reaction, when the elemental reactant is a metal, is ... 

Because the atoms of the pure element carbon are displacing (or replacing) the atoms of iron in iron(III) oxide, this is a single-displacement reaction. This particular reaction is used to isolate metallic iron from iron ore. 

An oxidation-reduction reaction is one in which electrons are transferred from one reactant to another. They are often called redox reactions for short. Oxidation is the loss of one or more electrons by a species. The species losing electrons is oxidized. Reduction is the gain of one or more electrons by a species, and that species is reduced. Oxidation and reduction always occur simultaneously. The single-displacement reaction of copper metal with silver nitrate solution is both a single replacement reaction and an oxidation-reduction reaction. 

Displacing One Element by Another Activity Series As we said, displacement reactions have the same number of reactants as products. We mentioned doubledisplacement (metathesis) reactions in discussing precipitation and acid-base reactions. The other type, single-displacement reactions, are all oxidation-reduction processes. They occur when one atom displaces the ion of a different atom from solution. When the reaction involves metals, the atom reduces the ion when it involves nonmetals (specifically halogens), the atom oxidizes the ion. Chemists rank various elements into activity series—one for metals and one for halogens— in order of their ability to displace one another. 

The element displaced from the compound is always the more metallic element—the one nearer the bottom left of the Periodic Table. The displaced element need not always be a metal, however. Consider a common type of single-displacement reaction, the displacement of hydrogen from water or from acids by metals. 

The displacement of hydrogen from water or acids is just one type of single-displacement reaction. Other elements can also be displaced from their compounds. For example, copper metal reduces aqueous solutions of ionic silver compounds, such as silver nitrate, to deposit silver metal. The copper is oxidized. 

The activity series can be used to predict which single-displacement reactions will take place. The elemental metal produced is always lower in the activity series than the displacing element. Thus, iron could be displaced from FeCl2 by zinc metal but not by tin. 

In 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 copperGO sulfate solution (by the way. Chapter 6 explains why copperGO sulfate is named the way it is — in case you re wondering), the zinc displaces the copper, as shown in this equation ... 

Some of the reactions you attempt may fail because the substances are not reactive or because the proper conditions for reaction are not present. For example, mer-cuiy(II) oxide does not decompose until it is heated magnesium does not bum in air or oxygen until the temperature reaches a certain point. When silver is placed in a solution of copper(II) sulfate, no reaction occurs. When copper wire is placed in a solution of silver nitrate, a single-displacement reaction takes place because copper is a more reactive metal than silver. (See Figure 8.1.)... 

DISPLACEMENT REACTIONS. In a displacement or single-displacement reaction, one element displaces another in a compound. For example, when metallic zinc is added to a solution of copper(II) chloride, the zinc replaces the copper. 

Some acids react with active metals and release hydrogen gas, H2. Recall that metals can he ordered in terms of an activity series. Metals above hydrogen in the series undergo single-displacement reactions with certain acids. Hydrogen gas is formed as a product, as shown by the reaction of barium with sulfuric acid. 

The rare-earth metal terbium is produced from terbium(lll) fluoride and calcium metal by the following single-displacement reaction ... 

The standard redox potential of the reaction CeS+ + 3e Ce is -2.2336 V. The metal undergoes single replacement reactions, displacing less electropositive metals from their salts in solution or melt ... 

Zinc metal reacts spontaneously with an aqueous solution of copper sulfate when they re placed in direct contact. Zinc, being a more reactive metal than copper (it s higher on the activity series of metals presented in Chapter 8), displaces the copper ions in solution. The displaced copper deposits itself as pure copper metal on the surface of the dissolving zinc strip. At first, the reaction may appecir to be a simple single replacement reaction, but it s also a redox reaction. 

These reactions are part of a larger category of reactions known as redox reactions (redox is short for oxidation-reduction). Sometimes these are called displacement reactions. These are chemical reactions in which atoms of one element replace the atoms of a second element in a compound. A general equation for a single-replacement reaction involving a metal (A), replacing a metallic cation in solution (B) is ... 

This experiment allows you to carry out the sequential conversion of copper metal to copper(II) nitrate to copper(II) hydroxide to copper(II) oxide to copper(II) sulfate and back to copper metal. This conversion is carried out using synthesis, decomposition, single displacement, and double displacement reactions. 

To predict which single substitution reactions will occur, we need to know a little about the relative reactivities of some of the important metals and nonmetals. Some metals and a few nonmetals are listed in Table 8.2 in order of decreasing reactivity. A more complete list is given in Section 17.2. Hydrogen is included in the list of metals because it can be displaced from aqueous acids by reactive metals (Figure 8.5) and can displace less active metals from their compounds ... 

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