Question

Aqueous solution of which of the following compounds is the best conductor of electric current?
A. ammonia, $N{{H}_{3}}$
B. fructose, ${{C}_{6}}{{H}_{12}}{{O}_{6}}$
C. acetic acid, ${{C}_{2}}{{H}_{4}}{{O}_{2}}$
D. hydrochloric acid, HCl

Answer 1

Hint: The compound which can dissociate itself completely will be the best conductor of electricity as the ions are mobile and lead to the flow of current which is nothing but electricity. So the compound that gives maximum ions is our correct option.

Complete answer:
-Based on the property of the compounds being able to dissociate into their ions, they are classified in 2 groups- electrolytes and non-electrolytes. Electrolytes are further classified as strong and weak electrolytes.
-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 anion. Bases are compounds that accept the ${{H}^{+}}$ion and convert into 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 solvent so that the ions can become mobile. Only then they can conduct electricity.
-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.
-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, $PbC{{l}_{2}}$
-Looking at the options we see that options B and C cannot be correct as fructose is a non-electrolyte and acetic acid is weak acid. So the answer has to be A or D as both of them are strong electrolytes.
-Ammonia is also a weak electrolyte because it is not able to dissociate in its ions due to high bond energy and so it gives ammonium ions but at a slow rate. HCl acid is a strong acid and it dissociates completely to give the ions which lead to formation of current. It can be shown as
     \[HCl\left( aq \right)\to {{H}^{+}}\left( aq \right)+C{{l}^{-}}\left( aq \right)\]

Therefore the correct option is D.

Note: Compounds which do not dissociate at all into its cation and anion are termed as non-electrolytes. They are different from electrolytes as they do not conduct electricity when placed in a galvanic cell while electrolytes conduct electricity.