Zinc 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 have seen that the single displacement reaction of zinc with copper(II) sulfate is a redox reaction, represented by the following chemical equation and net ionic equation. 

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. 

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 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 ... 

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. 

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. 

The lithium-copper oxide cell is voltage compatible (OCV = 1.5 V), i.e. it may be used as a direct replacement for conventional Leclanche or alkaline zinc cells. CuO has a particularly high volumetric capacity (4.2 Ah/cm3) so that cells are characterized by high specific energy -300 Wh/kg (700 Wh/dm3). The discharge curve shows a single step which may be attributed to the simple displacement reaction ... 

A factor that can influence C02 hydration/dehydration reactivity is the overall coordination number of the zinc center and the coordination mode of a bicarbonate ligand (Fig. 7). It is reasonable to suggest that a unidentate coordinated HCO will be easier to displace, which could influence the rate of the overall hydration reaction. Data discussed below in terms of single turnover experiments supports the notion that bidentate bicarbonate coordination inhibits catalytic C02 hydration. Similarly, bidentate coordination of HCO could be expected to slow the dehydration reaction. Notably, X-ray crystallographic studies of bicarbonate-bound forms of a mutant CA-II, and a Co(II)-substituted form of the enzyme, have revealed both monodentate and bidentate coordination modes for the bicarbonate anion.28,32,45... 

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