As a "rule of thumb" there are 20 drops of a liquid in a mL. Using this estimate and a density of 1.685, how many moles are in 27 drops of 85 % by weight phosphoric acid? Use the molecular weights that you already calculated. Give two significant digits and no extraneous marks.

0.020 mol

Explanation:

Let's consider the following relations:

20 drops of a liquid have a volume of 1 mL.The density of the solution is 1.685 g/mL, that is, each milliliter of solution has a mass of 1.685 g of solution.There are 85 g of phosphoric acid per 100 grams of solution (85 % by weight).The molar mass of phosphoric acid is 97.99 g/mol

With these relations, we can calculate the moles of phosphoric acid in 27 drops of solution.

What are the choices?

Idon’t know what the answer is i wish i could