What is the stoichiometric coefficient fo Ca in the reaction ?
`Ca+Al^(3+) rarr Ca^(2+)+Al`

Options

A. `2`
B. `1`
C. `3`
D. `4`

Answer

C

Explanation

Calcium is divalent , thus, it loses two `e^(-)` s:
(i) ` Ca rarr Ca^(2+) = 2e^(-)`
Aluminium is trivalent , thus , ` Al^(3+)` ion gains three electrons :
(ii) `Al^(3+) = 3e^(-) rarr Al`
Since oxidation and reduction occur simultaneously, we multiply Equation (i) by 3 and Equation (ii) by 2 so that number of electrons lost equals the number of electrons gained :
`{:([Ca rarr Ca^(2+)+2e^(-)]xx3),([Al^(3+)+3e^(-) rarr Al]xx2),(bar(3Ca+2Al^(3+)rarr3Ca^(2+)+2Al)):}`
Hence, the stoichiometric coefficient of Ca in the reaction is 3.