As an expert sommelier and brewer, I am well-versed in the world of solutions and concentrations. So let's dive into the question at hand: What is the molarity of a phosphoric acid solution that is 85% by mass H3PO4 and has a density of 1.7 g/mL?
To find the molarity of the solution, we first need to understand what molarity represents. Molarity is a measure of the concentration of a solute in a solution, expressed as the number of moles of solute per liter of solution. It is represented by the symbol “M”.
In this case, our solute is phosphoric acid (H3PO4), and our solution is 85% by mass H3PO4. This means that for every 100 grams of the solution, 85 grams are H3PO4.
To calculate the molarity, we need to know the number of moles of H3PO4 present in the solution. We can find this by dividing the mass of H3PO4 by its molar mass.
The molar mass of H3PO4 can be calculated by summing the atomic masses of its constituent elements: 3 hydrogen atoms (1.01 g/mol each), 1 phosphorus atom (30.97 g/mol), and 4 oxygen atoms (16.00 g/mol each). Summing these values gives us a molar mass of H3PO4 equal to 98.00 g/mol.
Now, let's calculate the number of moles of H3PO4 in the solution. We know that 85 grams of the solution is H3PO4, so we divide this mass by the molar mass of H3PO4:
85 g H3PO4 / 98.00 g/mol = 0.867 moles H3PO4
Now that we have the number of moles of H3PO4, we need to find the volume of the solution in liters. We are given the density of the solution, which is 1.7 g/mL. Density is defined as mass per unit volume, so we can rearrange this equation to solve for volume:
Density = Mass / Volume
Rearranging the equation, we find:
Volume = Mass / Density
In this case, the mass of the solution is not given, but we can assume a convenient value of 100 grams to simplify the calculation. So, the volume of the solution would be:
Volume = 100 g / 1.7 g/mL = 58.82 mL
To convert this volume to liters, we divide by 1000:
Volume = 58.82 mL / 1000 = 0.05882 L
Now that we have the number of moles of H3PO4 (0.867 moles) and the volume of the solution in liters (0.05882 L), we can calculate the molarity:
Molarity = moles of solute / volume of solution
Molarity = 0.867 moles / 0.05882 L = 14.74 M
Therefore, the molarity of the phosphoric acid solution is 14.74 M.
I hope this detailed explanation helps clarify the process of calculating the molarity of a solution. If you have any further questions or need clarification on any step, feel free to ask. Cheers!