In froth flotation, air is bubbled through an aqueous solution or slurry to which a foaming agent (soap) has been added. The air bubbles carry finely dispersed solids and hydrophobic materials such as grease and oil to the surface where they can be skimmed off in the foam an ore-containing slurry is to be processed in a froth flotation tank at a rate of 300 tons/h. The slurry consists of 20.0 wt% solids (the ore. SG = 1.2) and the remainder an aqueous solution with a density close to that of water. Air is sparged (blown through a nozzle designed to produce small bubbles) into the slurry at a rate of 40.0 ft³ (STP)/1000 gal of slurry. The entry point of the air is 10 ft below the slurry surface. The tank contents are at 75°F and the barometric pressure is 28.3 in Hg. The sparger design is such that the average bubble diameter on entry is 2.0 mm.

(a) What is the volumetric flow rate of the air at its entering conditions?

(b) By what percentage does the average bubble diameter change between the entry point and the slurry surface?