Statement - I : [Cu(CN)₄]^2– is more stable than [Cu(H₂O)₄]²⁺
Statement - II : On heating [Cu(H₂O)₄]²⁺ with NH₃, [Cu(NH₃)₄]²⁺ is formed.

  [Cu(CN)₄]^2–  , CN ^-  is a strong field ligand , CFSE  is high therefore  this compound is more stable 

 [Cu(H₂O)₄]²⁺ ,  H₂O is a  is a weak  field ligand  so CFSE  is less therefore  this compound is less stable 

 [Cu(H₂O)₄]²⁺ + 4 NH₃ $\stackrel{ }{\to }$[Cu(NH₃)₄]²⁺ + 4 H₂O