is there a bus from Luoyang to Kaifeng and how long is the ride?

Yes, you can take direct long-distance bus at Luoyang Bus Station, and get off at Kaifeng.
It takes around 3.5 hours on the way.
The schedules are 07:15, 08:25, 09:35, 10:45, 12:00, 13:00, 14:00 and 15:00.
And the ticket fare is CNY 60 per adult.

BTW, you can also travel between the two cities by train. The duration is about 3 hours and a hard seat costs CNY29.5.