Does the 2nd gen pencil work with the 9th gen iPad?

No. You cannot use a second generation Pencil with iPad9.

The first and second generation Pencil use an entirely different pairing and charging interface. 

The second generation Pencil can only be used with iPad models that have the magnetic/inductive dock that is exclusively designed for the Pencil. Charging and pairing is controlled automatically via the iPad magnetic dock; the second generation Pencil cannot be used with an iPad that features a Lightning connector.

The first generation Apple Pencil uses the physical Lightning port of the Pencil and host iPad for both pairing and charging the first generation Pencil. The first generation Pencil can also be charged using an inline charging adapter and the iPad’s Power Adapter. This pencil can only be used with compatible iPad models that have a Lightning connector; recent models of iPad that feature a USB-C port lack any means by which to pair with a first generation Pencil.

In summary, the Apple Pencil models are not interchangeable - and can only be used with the iPad that has appropriate internal hardware.

Here is the definitive compatibility list for Apple Pencil and iPad:

Apple Pencil compatibility - Apple Support

2nd gen Apple Pencil DOES NOT work with the base model 9th gen iPad.

You need to purchase and use the older 1st gen Apple Pencil, with the top, removable, magnetic Lightning connector protective cap, instead.

Both Pencil charge and pair differently.