\(KI + I _2 \rightarrow KI _3\)

The shape of \(KI _3\) is determined as the tri-iodide ion \(I _3{ }^{-}\) and \(K ^{+}\)exist linearly.

Here, shape of tri-iodide ion is:

Lone pair \(=3\)

bond pair \(=2\)

Hybridization \(= sp ^3 d\)

structure \(=\) Trigonal bipyramidal

Shape \(=\) linear (two bond pair only)

Hence, shape is linear