Question

$BaC{l}_2$ dissociates in water to give one $B{a}^{2+}$ ion and two $C{l}^{-}$ ions. If concentrate $HCl$ is added to this solution:
A.[$B{a}^{2+}$] increases
B.[$B{a}^{2+}$] remain constant
C.[$O{H}^{-}$] increases
D.The number of moles of undissociated $BaC{l}_2$ increases.

Answer 1

Hint: As per Le chatelier’ s principle, when a system existing in equilibrium subjects to a change in concentration, temperature, or pressure, an equilibrium shift in a direction that negates the effect of the change is observed.

Complete step by step answer:
We will utilize Le chatelier’ s principle for the solution of the above question. On dissolving in water, $BaC{l}_2$ gets dissociate into one barium ion and two chloride ions as:
$$BaC{l}_2\rightleftharpoons B{a}^{2+}+2C{l}^{-}$$
When we add $HCl$into the aqueous solution of $BaC{l}_2$, then $HCl$ get dissociate in one hydrogen ion and one chloride ion as:
$HCl\to H^{+}+C{l}^{-}$
As a result, there is an increase in the concentration of chloride ions in the solution. But according to Le chatelier’ s principle, when a system is subjected to any change in concentration then the system readjusts itself to undo the change imposed. In this case, if there is an increase in the concentration of chloride ion, then the system will try to decrease the concentration of chloride ions as a result the equilibrium shifted in the backward direction which increases the number of moles of undissociated $BaC{l}_2$.
Hence the correct answer is option D..

Additional information: According to the IUPAC naming convention, annulenes with seven or more than seven carbon atoms are named as [n] annulene, where n describes the number of a carbon atom in the ring. Annulene may be aromatic, non aromatic, or antiaromatic.

Note:
Some application of Le chatelier’ s principle are discussed below:
Le chatelier’ s principle is an observation about the chemical equilibria of reaction.it is very useful for predicting the condition of concentration, temperature, and pressure to get the higher yield in certain industrial reactions such as Haber's process used for the manufacture of ammonia, contact process used for the manufacture of sulphuric acid, etc.
We can also predict the changes in solubility of the substances with temperature change.