Question

On passing a current of HCl gas in a saturated solution of NaCl the solubility of NaCl
A. Increase
B. Decrease
C. Remain unchanged
D. NaCl decomposes

Answer 1

Hint: Saturated solution of the NaCl is the solution containing soluble NaCl and when electric current of HCl gas is passed to solution thus, the solution get charged and thus, soluble NaCl get ionised as \[N{{a}^{+}}\]and \[C{{l}^{-}}\]. Now the solution contains \[C{{l}^{-}}\]ions in large amounts due to ionisation of HCl gas and NaCl salt. Due to the large number of \[C{{l}^{-}}\] ions in the solution, the common ion effect comes into play.

Complete Step by Step Answer:
When electric current is passed to a solution (electrodes due to which current is following is anode and cathode). In electrochemistry anode electrode is positively charged and cathode electrode is negatively charged.

Now in this question we passed current of HCl gas means in this \[{{H}^{+}}\]ion will act as anode electrode and \[C{{l}^{-}}\] ion will act as cathode electrode. When this current is passed into saturated solution of NaCl, the NaCl gets ionised due to its conducting nature as \[N{{a}^{+}}\] and \[C{{l}^{-}}\].

Now \[C{{l}^{-}}\]of NaCl run towards anode electrode (\[{{H}^{+}}\] electrode) and \[N{{a}^{+}}\]run towards cathode electrode (\[C{{l}^{-}}\] electrode) as opposite charges attract each other. From this we can say NaCl crystals form from its ionizable or dissolved form.

In short we can say that due to accumulation of large number of \[C{{l}^{-}}\] ions, \[C{{l}^{-}}\] prefer to form bond with NaCl due to common ion effect or due to repulsion effect. Thus, the crystal of NaCl started to form and is no more soluble in solution. Then this insoluble salt, NaCl, precipitates and settles down to the bottom.
Thus, the correct option is B.

Note: As NaCl is a salt which increases the conductivity of solution by ionisation when dissolved in solution even when solution itself is not conducting like pure water and sugar solution. This is a method of conduction of electricity due to ions but not by free electrons.