The chain can only move at one linear speed over either sprocket. So we know the radius and angular speed of the front sprocket, thus

(where the subscript "f" repesents the front sprocket.)

We now know the linear speed of the chain so we can calculate the angular speed of the rear sprocket:

Now we can calculate the centripetal acceleration of the chain as it goes around the rear sprocket:

Hint: Stick to the basics when problem solving. I don't even recognize that formula you posted.

-Dan