an acid compound found in plants and vegetables such as rhubarb, has a mass percent composition of 26.7% c, 2.24% h, and 71.1% o. it can interfere with respiration and cause kidney or bladder stones. if a large quantity of rhubarb leaves is ingested, this acid can be toxic. the lethal dose (ld50) in rats for this acid is 375 mg/kg. rhubarb leaves contain about 0.5% by mass of the acid. what is the empirical formula of the acid?

Ateacher attaches a ball to a meter long string and whirls it around in a horizontal circle at constant speed. the teacher explains that the string is what makes the ball go in a circle. why is the string necessary? a) the string is needed to apply a torque to the ball. b) the string is needed to push on the ball to get it up to speed. c) circle motion requires an inertia which is provided by the string. d) circle motion requires a force to give it a centripetal acceleratio