In which of the pairs of ions given, there is an ion that forms a co-ordination compound both aqueous sodium hydroxide and ammonia and another ion that forms a co-ordination compound only with aqueous sodium hydroxide ?

Options

A. `Pb^(2+), Cu^(2+)`
B. `Zn^(2+), Al^(3+)`
C. `Cu^(2+), Zn^(2+)`
D. `Al^(3+), Cu^(2+)`

Answer

B

Explanation

` Zn ^ ( 2 + ) , Al^( 3 + ) `
(i) `Zn (OH ) _ 2 + 2NaOH to Na [Zn ( OH ) _4 ]^( 2- ) + 2 Na^( + ) `
` underset ( "Anhydrous")(ZnCl_ 2 ) + 4NH _ 3 to underset ( "Tetrammine zinc chloride") ( Zn ( NH _ 3 ) _ 4 ) + Cl _ 2 `
(ii) `Al ( OH ) _ 3 + NaOH to [Al ( OH) _ 4]^( - ) `
` Al^( 3 + ) + 3NH _ 3 to Al ( NH _ 3 ) _ 3 `