Calculate the molarity

Question

Calculate the molarity of a solution prepared by dissolving 12.6 g of Na2CrO4 in enough water to produce a solution with a volume of 640. mL .
Express the molarity to three significant digits.

Answer 1

Molarity = moles of solute / liters of solution

 

First, change the 12.6 g to moles.

 

(1) moles = grams/ molar mass of Na2CrO4

(Use the Periodic Table)

 

(2) Express the volume 640 mL in Liters.

 

Substitute in the expression for molarity       

Molarity = (1)/(2)

 

Express your final answer to 3 significant digits.