Answer
$CO_2$ is a Lewis acid.
Work Step by Step
Oxides formed by a nonmetal are considered Lewis acids.
This happens because, as we've learned in section 14-9b, if the molecule has a pi bond in its central atom, and this atom is slightly positively charged**, it can receive one lone pair of electrons.
** Since oxygen is very electronegative, it attracts the electrons in the bond, making the central atom slightly positive.
Receiving one lone pair of electrons, it is considered a Lewis acid.
