Chemistry

Electrolysis, Electrolyte, Electrode, Anode and Cathode

Nini Ezeugo - Thu, 23rd May, 2019 @ 22:13: PM



Introduction to Electrolysis:

To get a better understanding of electrolysis, we need to first understand what ions are. The reason is because electrolysis involves the behavior ions in solution.

Simply put, ions are charged atoms

For instance, group one elements have 1 valence electron and will undergo chemical reaction by donating it out to attain an octet or duplet configuration. A positively charged ion or cation is formed as a result. Sodium atom (Na) will give out its 1 valence electron to form sodium ion (Na+)

Conversely, group seven elements have 7 valence electrons and will undergo a chemical reaction by accepting one electron to attain an octet configuration. A negatively charged ion or  anion is formed as a result. Chlorine atom (Cl) will accept 1 electron from a group 1 element (e.g sodium) to for chlorine ion (Cl-)

Please read our article on periodic table and classification of elements here.

Note: Valence electron(s) is the number electron(s) on the outermost shell of an atom. An octet or duplet configuration is a state where atoms or ions have the maximum of eight or two valence electrons. They are stable as a result and do not need further reaction with any other element.

 

As we advance in this topic, Certain terms will be used often; so understanding them is important. These terms include:

 

  • Electrolyte

They are solutions or molten compounds or paste like compounds that conduct electricity. Electrolytes are composed of ions.

Note: Solids that conducts electricity are called conductors. You may read our article on the physical properties of metals here.

Electrolytes will dissociate into its constituent ions and will migrate to their respective electrodes when an electric current is passed through it. The strength of dissociations of the ions present in an electrolyte will determine whether the electrolyte is strong or weak.

Strong electrolyte: They dissociate completely into their constituent ions when electricity is passed through them. Example of strong electrolyte are KCl(aq) (potassium chloride) and Ca(OH)2(aq) (calcium hydroxide).

Weak electrolyte: They dissociate partially into their constituent ions when electricity is passed through them. Examples of weak electrolytes are Ethanoic acid (CH3COOH) and Mercury chloride (HgCl)

 

The ions that are dissociated in an electrolyte are of two types:

  • Cation

A cation is a positively charged ion. Examples are Na+, H+, K+, Mg2+, Ca2+ and so on. They will move to the negative electrode during electrolysis. This negative electrode in electrolysis is referred to as the ANODE.

 

  • Anion

An anion is a negatively charged ion. Examples are Cl-, F-, O2- and OH-. They will move to the positive electrode during electrolysis. This positive electrode in electrolysis is referred to as the CATHODE.

 

  • Electrodes

These are rods or plates that connect an electrical circuit to the electrolyte; thus becoming the avenues through which electric current enters or leaves the electrolyte. They are in contact the electrical circuit at one end and with the electrolyte at the other end. They are of two types;

  1. Cathode: This is the positive electrode through which electric current enters the electrolyte. The cathode will attract negatively charged ions (anions) during electrolysis (or when current is passed through the electrolyte).
  2. Anode: This is the negative electrode through which electric current leaves the electrolyte. The anode will attract positively charged ions (cations) during electrolysis (or when current is passed through the electrolyte).

 

  • Electrolysis

This is the process of passing electricity into an electrolyte (through the electrodes), with the resultant decomposition of the electrolyte. The decomposition of the electrolyte imply that the electrolyte is broken down into it constituents elements.

 

Ionic Theory

An electrolyte dissociates into two types of ions; a cation and an anion.

YZ -> A+ + B-

KCl -> K+ + Cl-

Ideally, the electrolyte (YZ or KCl) from the above instance should already be in an aqueous form (see the definition of an electrolyte above). So the above equation can be correctly re-written as

Y+Z-(aq) -> Y+(aq) + Z-(aq)

K+Cl-(aq) -> K+(aq) + Cl-(aq)

Note: The process of splitting of molecules in an electrolyte into ions is known as ionization or dissociation. All electrolytes do not ionize to the same degree since some electrolytes may be strong (ionizes or dissociates completely) while others may be weak (ionizes or dissociates partially)

The ionic theory of electrolysis states that substances whose solution conducts electricity will undergo electrolytic dissolution or dissociation or ionization.

Topics in Chemistry

Physical and Chemical properties of Acids Matter, Mass and Weight Interesting facts about Gold Differences between Molecular Mass and Molar Mass Introduction to Organic Chemistry Emperical Formula explained with worked example Periodic table and Classification of Elements Daltons Atomic Theory and its Modifications Physical Properties of Metals Grahams law of diffusion




Topics in Chemistry

Physical and Chemical properties of Acids Matter, Mass and Weight Interesting facts about Gold Differences between Molecular Mass and Molar Mass Introduction to Organic Chemistry Emperical Formula explained with worked example Periodic table and Classification of Elements Daltons Atomic Theory and its Modifications Physical Properties of Metals Grahams law of diffusion



THANKS FOR READING THIS POST.
YOU NEED TO BE REGISTERED TO MAKE COMMENTS
PLEASE REGISTER HERE