Anurse practitioner prepares an injection of promethazine, an antihistamine used to treat allergic rhinitis. if the stock bottle is labeled 30.mg/ml and the order is a dose of 10.0mg, how many milliliters will the nurse draw up in the syringe?

With a dose order of 10mg and the stock bottle being labeled 30mg/mL, the nurse will need to draw up .33mL. We come to this answer by taking the dose order of 10mg and multiplying by the stock bottle amount of 1mL/30mg. The 30mg/mL was inverted to account for units so that mg cancels out and we are left with mL answer.
Total mL needed = 10mg * (1mL/30mg) = .33mL

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.