When zinc metal is submerged into a quantity of aqueous \(\ceHCl\), the adhering to reaction occurs (Figure \(\PageIndex1\)):

\<\ceZn (s) + 2HCl (aq) → H2 (g) + ZnCl2(aq) \labeleq:1\>

This is one instance of what is sometimes called a single replacement reaction because \(\ceZn\) replace instead instead \(\ceH\) in combination with \(\ceCl\).

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Example \(\PageIndex1\): Reducing silver Ions

Write and also balance the oxidation reaction that has actually silver ions and aluminum metal as reactants and also silver metal and also aluminum ions as products. Recognize the problem oxidized, substance reduced, reduce agent and also reducing agent.


We begin by using signs of the elements and also ions to represent the reaction:

\<\ceAg^+ + Al → Ag + Al^3+ \nonumber\>

The equation looks balanced as the is written. However, once we compare the as whole charges on each side the the equation, we find a charge of +1 on the left but a charge of +3 on the right. This equation is not appropriately balanced. Come balance it, let us write the two half reactions. Silver ions space reduced, and it bring away one electron to change Ag+ come Ag:

Reduction half-reaction: \<\ceAg^+ + e^− → Ag \nonumber\>

Aluminum is oxidized, shedding three electron to adjust from Al to Al3+:

Oxidation half-reaction: \<\ceAl → Al^3+ + 3e^− \nonumber\>

To incorporate these two half reactions and cancel out all the electrons, we have to multiply the silver reduction reaction by 3:


Exercise \(\PageIndex1\)

Write and balance the oxidization reaction that has calcium ions and also potassium metal as reactants and calcium metal and potassium ion as products. Determine the problem oxidized, problem reduced, reduce agent and also reducing agent.


Reduction: Ca2+ + 2e− → Ca

Oxidation: 2 (K → K+ + e−)

Combined: Ca2+ + 2K → Ca + 2K+

The substance oxidized is the reactant that had undergone oxidation: K The substance reduced is the reactant that had actually undergone reduction: Ca2+ The reducing certified dealer is the exact same as the substance oxidized: K The oxidizing agent is the same as the problem reduced: Ca2+

Potassium has actually been used as a reducing agent to attain various metals in your elemental form.

To your Health: redox Reactions and Pacemaker Batteries

All batteries use redox reaction to supply electricity because electricity is basically a stream of electron being transferred from one substance to another. Pacemakers—surgically implanted tools for regulation a person’s heartbeat—are it is provided by tiny batteries, so the appropriate operation of a pacemaker relies on a oxidization reaction.

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Pacemakers provided to be powered by NiCad batteries, in i beg your pardon nickel and cadmium (hence the name of the battery) react through water follow to this oxidization reaction:

\<\ceCd(s) + 2NiOOH(s) + 2H2O(ℓ) → Cd(OH)2(s) + 2Ni(OH) 2(s) \nonumber\>

The cadmium is oxidized, when the nickel atom in NiOOH space reduced. Except for the water, every the building material in this reaction are solids, permitting NiCad batteries to be recharged thousands of times before they protect against operating. Unfortunately, NiCad batteries are fairly heavy batteries to it is in carrying around in a pacemaker. Today, the lighter lithium/iodine battery is provided instead. The iodine is liquified in a hard polymer support, and the in its entirety redox reaction is as follows:

\<\ce2Li(s) + I2(s) → 2LiI (s) \nonumber\>

Lithium is oxidized, and also iodine is reduced. Back the lithium/iodine battery cannot be recharged, among its advantages is the it lasts as much as 10 years. Thus, a human with a pacemaker does not have to worry about periodic recharging; about once per te a human requires minor surgery to replace the pacemaker/battery unit. Lithium/iodine battery are also used to power calculators and watches.

Figure \(\PageIndex1\): A little button battery favor this is supplied to power a watch, pacemaker, or calculator. (CC BY-SA; Gerhard H Wrodnigg via Wikipedia)