the ketone contains c=o bond where c+ and 0- partial charge is there and the bond is essentially a 1 and a half bond in resonance and hence the hydrogen is loosely attached as the c adjacent to c=o is -ve and hence removing h as h+ is easy whereas alkanes are nonpolar and no such way of removing h.thus ketones are more acidic.remember ease of removing h as h+ is condition for acidity.