Question

Which one of the following is a strong electrolyte?
(A) \[PbB{{r}_{2}}\]
(B) \[CuC{{l}_{2}}\]
(C) ${AgN}{O}_{3}$
(D) All of the above

Answer 1

Hint: We cannot find the strength of electrolyte just by looking at the chemical formulae of the compounds as there are many variations in finding if an electrolyte is strong or weak. Also, there are several types of compounds that can act as an electrolyte like acids, bases as well as salts.

Complete step by step solution:
-Before answering about the strength of an electrolyte, let us first talk about what an electrolyte is. An electrolyte is a compound which dissociates into its constituent ions, cation and anion in presence of DC current under the process of electrolysis.
-Many types of compound can be used as electrolytes but the most preferred compounds are acids, bases and salts.
-Acids are the compounds that donate ${{H}^{+}}$ion to become an anion. Bases are compounds that accept the ${{H}^{+}}$ion and convert into a cation. Salts are the compounds formed mainly by the reaction of acids and bases.
-Electrolytes dissolve in water to form a solution and that solution conducts electricity by dissociating into ions.
Eg. $NaCl\left( s \right)\to N{{a}^{+}}\left( aq \right)+C{{l}^{-}}\left( aq \right)$
Water is added as a solvent so that the ions can become mobile. Only then they can conduct electricity.
-Now coming to the strength of the electrolytes. There are two types of electrolytes, strong and weak. Strong electrolytes are those which can dissociate to a very large extent to give the respective cations and anions. Weak electrolytes are those which dissociate very less and so the ions formed are not much which reduces the conductivity of the solution.
-Dissociation of strong electrolytes is shown by a forward arrow and that of weak electrolytes is shown by double arrows.
$NaCl\left( s \right)\to N{{a}^{+}}\left( aq \right)+C{{l}^{-}}\left( aq \right)$
It signifies that this electrolyte is a strong electrolyte.
\[{{H}_{2}}O\rightleftarrows {{H}^{+}}+O{{H}^{-}}\]
It signifies that water is a weak electrolyte.
-If we want to talk about the strength of the electrolytes, we need to see if the compound is acid, base or salt first. Then we need to see if it is a strong acid/base or a weak acid/base. Generally strong acids and bases are strong electrolytes because they completely lose/gain ${{H}^{+}}$ion and so dissociate completely.
Weak acids/bases are weak electrolytes as they are not able to lose/gain ${{H}^{+}}$ion easily, thus, they do not dissociate properly into cation and anion.
-Salts are formed by the reaction of acids and bases. So they are generally treated as strong electrolytes as they can dissociate into their respective ions which came from the original acid and base. Thus generally all salts are strong or good electrolytes. Some salts are so strong they dissociate even in solid form.
-Some examples of acids as strong electrolytes are HCl, HBr, HI, $HCl{{O}_{4}},{{H}_{2}}S{{O}_{4}}$ and acids as weak electrolytes are $C{{H}_{3}}COOH,HF,{{H}_{2}}C{{O}_{3}},{{H}_{3}}P{{O}_{4}}$
-Some examples of bases as strong electrolytes are $NaOH$, $KOH$, $LiOH$, $Ca{{\left( OH \right)}_{2}}$ and bases as weak electrolytes are ammonia, pyridine.
-Some examples of salts as strong electrolytes are $NaCl$, $KCl$, $N{{H}_{4}}Cl$ and salts which are weak electrolytes are $AgCl$, $PbC{{l}_{2}}$
-The strength of electrolytes can be measured by the value of their electrical conductance obtained by dissolving the substances in water.

Therefore, all of the above electrolytes are strong electrolytes. So the correct option is (D) All of the above.

Note: The compounds which do not dissociate at all into its cation and anion are termed as non-electrolytes. Do not confuse it with weak electrolytes. Weak electrolytes do dissociate themselves, though very less. Eg includes glucose, fructose, sucrose, galactose, etc. Also, there are certain ionic compounds which are thought to be strong electrolytes but in reality are weak electrolytes as they cannot dissociate themselves completely into their ions. They dissociate a few of their ions only. Eg ${{K}_{2}}S{{O}_{4}},$