JEE Advanced 2026 · Paper 2, Chemistry question 13

Put ligands at $\pm x,\pm y,\pm z$. Each of the 8 faces takes one vertex from each axis.

cis-$\ce{[Co(NH3)4Cl2]+}$ (Cl at $+x,+y$). A face with two Cl must contain both, and the edge $(+x,+y)$ lies in exactly two faces, completed by $+z$ or $-z$ (both N). 2 faces.

mer-$\ce{[Co(NH3)3Cl3]}$ (Cl at $+x,-x,+y$; N at $-y,\pm z$). Every face has one $x$-vertex (Cl) and one $z$-vertex (N). It has two Cl exactly when its $y$-vertex is $+y$. That gives $2\times2=$ 4 faces.

Total $2+4=6$.