How to calculate the molarity of phosphoric aci9d in a solution that is 84% by mass phosphoric acid and a density of 1.87 g/ml

Answer 1

84% by mass H3PO4 means 84 g H3PO4 in 100 g solution. M = moles/L.
How many moles are in 84g H3PO4? That is 84/molar mass H3PO4.
What is the volume of 100 g soln.
mass = volume x density. You know mass and density, solve for volume.
Then M = #moles/L