Is this b85 Mobo capable of running an i5 4690k?

The prob is depending on the BIOS thats on it now (if you've got it).

Look at the sticker on the mobo. The last 4 numbers is the BIOS thats on it

If it's under 2001, unless this mobo supports USB BIOS flashback, (it doesn't), there's no way to update it

Unless you buy / borrow a CPU that the BIOS you have now supports flash it then put this one in