Calculate the molarity of 3 drops (0.15mL) of a 0.5M Na3PO4 solution after adding 15 drops (.75mL) of water.

Question

(Presume drops are the same size, one drop = 0.05mL)((Presume volumes are additive))

So far I've figured .15g Na3PO4/163.94g/mol Na3PO4 = .0009moles

.75g H20/18.015 = 0.0416 mol H20

What are the next steps to solve this problem? Thank you!

Answer 1

you are diluting the sodium phosphate by a factor of .90/.15=6

that means, the new molarity is .5/6

Answer 2

Thanks Bob!

Curious where .90 comes from? .0009molX1000mL?

.5/6= .083M