question_answer

Write half cell reactions and balanced chemical equations for the following galvanic cells? (a) \[Zn(s)+|Z{{n}^{2+}}(aq)||\,C{{r}^{3+}}\,(aq)\,|Cr(s)\] (b) \[Pb(s),\,PbS{{O}_{4}}(s)|HSO_{4}^{-}(aq),\] \[{{H}^{+}}(aq)||{{H}^{+}}(aq),\,HSO_{4}^{-}(aq)\,|Pb{{O}_{2}}(s),\]\[PbS{{O}_{4}}(s)\] (c) \[Mg(s)|M{{g}^{2+}}(aq)||S{{n}^{2+}}(aq)|Sn(s)\].

Answer:

                (a)                                          \[Zn(s)\xrightarrow{\,}\,Z{{n}^{2+}}(aq)+2{{e}^{-}}]\times 3\]                   (Oxidation half reaction) \[C{{r}^{3+}}(aq)+3{{e}^{-}}\xrightarrow{\,}Cr(s)]\,\times 2\]                                     (Reduction half reaction) _______________________________________________ \[3Zn(s)+2C{{r}^{3+}}(aq)\xrightarrow{\,}\,3Z{{n}^{2+}}(aq)+2Cr(s)\] (b)     \[Pb(s)+HS{{O}^{-}}_{4}(aq)+{{H}_{2}}O\xrightarrow{\,}PbS{{O}_{4}}(s)+{{H}_{3}}{{O}^{+}}(aq)\]                 (Oxidation half reaction) \[Pb{{O}_{2}}(s)+3{{H}_{3}}{{O}^{+}}(aq)+2HSO_{4}^{-}\,+2{{e}^{-}}\xrightarrow{\,}PbS{{O}_{4}}(s)+3{{H}_{2}}O+2{{e}^{-}}\]         (Reduction half reaction) ____________________________________________________________ \[Pb(s)+3HSO_{4}^{-}(aq)+Pb{{O}_{2}}(s)+2{{H}_{3}}{{O}^{+}}(aq)\]\[\xrightarrow{\,}\,2PbS{{O}_{4}}(s)+4{{H}_{2}}O\]. (c)                                                           \[Mg(s)\xrightarrow{{}}\,M{{g}^{2+}}(aq)+2{{e}^{-}}\]  (Oxidation half reaction) \[S{{n}^{2+}}(aq)+2{{e}^{-}}\xrightarrow{\,}\,Sn(s)\]                                                      (Reduction half reaction)                                 _________________________________________________ \[Mg(s)+S{{n}^{2+}}(aq)\xrightarrow{\,}\,M{{g}^{2+}}(aq)+Sn(s)\]