Q4.45 - Chemistry: Molecular Nature Of Matter And Change

Question

 Do either of the following reactions go to completion? If so, what factor(s) cause(s) each to do so? 

1.   ${\mathrm{MgSO}}_3\left(\mathrm{s}\right)+2\mathrm{HCI}\left(\mathrm{aq}\right)\to {\mathrm{MgCI}}_2\left(\mathrm{aq}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}$
2.  $3\mathrm{Ba}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+2{\mathrm{H}}_3{\mathrm{PO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Ba}}_3{\left({\mathrm{PO}}_4\right)}_2\left(\mathrm{s}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{I}\right)$

 

Step-by-Step Solution

Answer

Answer

 

(a)  ${\mathrm{MgSO}}_3\left(\mathrm{s}\right)+2\mathrm{HCI}\left(\mathrm{aq}\right)\to {\mathrm{MgCI}}_2\left(\mathrm{aq}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}$

     This reaction goes to completion.

(b)  $3\mathrm{Ba}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+2{\mathrm{H}}_3{\mathrm{PO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Ba}}_3{\left({\mathrm{PO}}_4\right)}_2\left(\mathrm{s}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{I}\right)$

     This reaction goes to completion

 

Step 1: Determine the situation of the completion of the reaction

If the reaction is irreversible and all the reactants are consumed in the reaction then the reaction becomes complete.

Step 2: Determine factors which causes completion of the reaction

${\mathrm{MgSO}}_3\left(\mathrm{s}\right)+2\mathrm{HCI}\left(\mathrm{aq}\right)\to {\mathrm{MgCI}}_2\left(\mathrm{aq}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}$

In the above reaction, sulphur dioxide ${\mathrm{SO}}_2$  is formed which can escape from the system and water is formed. Hence the reaction is irreversible which means the reaction goes to completion.

(b)The formation of a precipitate  makes the backward reaction impossible. Apart from that water is also formed which is a non -electrolyte. Therefore, the reaction cannot go to completion.