Falsity rhymes with:
analyticity, animosity, atrocity, audacity, biodiversity, capacity, complexity, complicity, curiosity, density, diversity, domesticity, eccentricity, elasticity, electricity, felicity, ferocity, generosity, incapacity, intensity, laxity, monstrosity, necessity, obesity, opacity, overcapacity, paucity, perplexity, perversity, publicity, religiosity, simplicity, specificity, toxicity, university, velocity, viscosity, voracity
Falsity sounds like:
falgoust, falgout, falsehood, falsetto, felicetti, felicitate, felicite, felicity, filched, filegate, flaccid, flagday, flagged, flashed, flashiest, flaxseed, fleeced, fleshed, flexed, flight, flighty, flocked, fluctuate, fluctuated, flushed, full-sized, fullest