The calculated distance (air line) between Groningen and Alphen aan den Rijn is approximately 110 miles respectively 177 kilometers.
By car or train, the actual journey to Alphen aan den Rijn is certainly longer, as only the direct route (as the crow flies) between Groningen and Alphen aan den Rijn has been calculated here.
Air line (approximately)
177 kilometers
95 nautical miles