How to Calculate the Molarity of Phosphoric Acid in a Solution?

What is the molarity of phosphoric acid in a solution labelled 20.0% phosphoric acid (H3PO4) by weight with a density = 1.12 g/mL?

Can you explain the step-by-step process to find the molarity of phosphoric acid in the given solution?

Final Answer:

The molarity of phosphoric acid in the solution is approximately 5.85 M.

Explanation:

To find the molarity of phosphoric acid in the solution, we need to follow these steps:

1. Calculate the mass of phosphoric acid (H3PO4) in the solution:
• - Given that the solution is labeled as 20.0% phosphoric acid by weight, we can assume that 20.0 g of H3PO4 is present in 100 g of the solution.
2. Calculate the number of moles of H3PO4:
• - To do this, divide the mass of H3PO4 by its molar mass (97.994 g/mol).
3. Calculate the volume of the solution in liters:
• - Given the density of the solution is 1.12 g/mL, we can convert it to 1120 g/L (since 1 mL = 1 g).
4. Calculate the molarity (M):
• - Divide the number of moles of H3PO4 by the volume of the solution in liters.

Now, let's calculate it step by step:

1. Mass of H3PO4 in the solution = (20.0% / 100%) x 100 g = 20 g
2. Moles of H3PO4 = 20 g / 97.994 g/mol ≈ 0.204 moles
3. Volume of the solution = 1120 g / 1 g/mL = 1120 mL = 1.12 L
4. Molarity (M) = 0.204 moles / 1.12 L ≈ 5.85 M

So, the molarity of phosphoric acid in the solution is approximately 5.85 M.

Phosphoric acid, also known as orthophosphoric acid, is a mineral acid which has the chemical formula H3PO4. It is a colorless, odorless liquid that is highly soluble in water. The molarity of a solution is a measure of the concentration of a solute in a solvent.

In this case, to calculate the molarity of phosphoric acid in the given solution labeled 20.0% phosphoric acid by weight with a density of 1.12 g/mL, we need to determine the mass of phosphoric acid, the number of moles of H3PO4, the volume of the solution, and finally the molarity.

By following the step-by-step calculation process as explained above, we can determine that the molarity of phosphoric acid in the solution is approximately 5.85 M.

This calculation is essential in various fields such as chemistry, pharmacy, and research where accurate concentration measurements are required for specific reactions or analyses.