Question

You need to make an aqueous solution of 0.139 M potassium phosphate for an experiment in lab, using a 250 mL volumetric flask. How much solid potassium phosphate should you add? _______g

Answer 1

Answer:

7,38 g of K₃PO₄

Explanation:

Molarity is an unit of chemical concentration. 0,139 M means 0,139 moles of solute per liter of solution.

In this case, the solute is potassium phosphate (K₃PO₄; molar mass: 212,27 g/mol) and the volume of the solution must be 250mL≡0,25L.

Thus, the moles of potassium phosphate you need are:

0,139 mol/L×0,25L = 0,03475 moles of K₃PO₄

In grams:

0,03475 moles of K₃PO₄ × $\frac{212,27g}{1mol}$ = 7,38 g of K₃PO₄

I hope it helps!