The molarity of 1 L orthophosphoric acid (H₃PO₄) having 70% purity by weight (specific gravity 1.54 g cm⁻³) is _____

Orthophosphoric Acid Molarity | JEE Mains PYQ | Mole Concept

Q. The molarity of 1 L orthophosphoric acid (H₃PO₄) having 70% purity by weight (specific gravity 1.54 g cm⁻³) is ______ M.

Explanation

Step 1: Calculate mass of solution

Volume = 1 L = 1000 mL
Density = 1.54 g mL⁻¹
Mass of solution = 1000 × 1.54 = 1540 g

Step 2: Calculate mass of pure H₃PO₄

Purity = 70%
Mass of H₃PO₄ = 70/100 × 1540 = 1078 g

Step 3: Calculate number of moles of H₃PO₄

Molar mass of H₃PO₄ = 98 g mol⁻¹
Moles = 1078 ÷ 98 ≈ 11

Step 4: Calculate molarity

Molarity = Moles / Volume (in L)
M = 11 / 1 = 11 M

Correct Answer = 11

Previous Year Questions – Mole Concept