An aqueous solution of phosphoric acid, H3PO4, contains 285 g H3PO4 in 400 mL solution, and has a density of 1.35 g/mL. Calculate
a. the weight % H3PO4 in this solution.
b. the concentration in mol/L of this solution
If it contains 285 g in 400 mL how much is in 1 L?
285 x (1000/400) = 712.5 g H3PO4 in 1 L.
How much does 1 L weigh? It has a mass of
1.35 g/mL x 1000 mL = 1350 grams.
So the mass% is (mass H3PO4/mass solution)*100 = ??
How many moles H3PO4 in that 712.5 g H3PO4. That is moles = grams/molar mass.
Then M = moles/L of solution and that 712.5 g IS for 1 L of solution.
Check my work.
53.54
To calculate the weight % H3PO4 in the solution, we need to find the ratio of the weight of H3PO4 to the weight of the whole solution, then multiply by 100. Here's how you can do it:
a. Calculating the weight % H3PO4:
Step 1: Find the weight of H3PO4 in the solution.
Given that the density of the solution is 1.35 g/mL, you can calculate the weight of the solution using the volume and density:
Weight of the solution = Volume of the solution × Density of the solution
Weight of the solution = 400 mL × 1.35 g/mL = 540 g
Step 2: Calculate the weight % H3PO4.
To find the weight of H3PO4 in the solution, divide the weight of H3PO4 by the weight of the whole solution, then multiply by 100:
Weight % H3PO4 = (Weight of H3PO4 / Weight of the solution) × 100
Weight % H3PO4 = (285 g / 540 g) × 100
Weight % H3PO4 ≈ 52.78%
So, the weight % H3PO4 in the solution is approximately 52.78%.
b. Calculating the concentration in mol/L (also known as molarity) of the solution:
To calculate the molarity, we need to convert the weight of H3PO4 to moles, and then divide by the volume of the solution in liters.
Step 1: Convert the weight of H3PO4 to moles.
To convert grams of a substance to moles, we need to divide by its molar mass. The molar mass of H3PO4 can be calculated as:
Molar mass of H3PO4 = (3 × atomic mass of H) + (1 × atomic mass of P) + (4 × atomic mass of O)
Molar mass of H3PO4 = (3 × 1.01 g/mol) + (1 × 31.0 g/mol) + (4 × 16.00 g/mol)
Molar mass of H3PO4 = 97.99 g/mol
Now, we can calculate the number of moles of H3PO4 present in the solution:
Number of moles of H3PO4 = Weight of H3PO4 / Molar mass of H3PO4
Number of moles of H3PO4 = 285 g / 97.99 g/mol
Number of moles of H3PO4 ≈ 2.91 mol
Step 2: Calculate the concentration in mol/L.
To find the concentration, divide the number of moles of H3PO4 by the volume of the solution in liters:
Concentration (mol/L) = Number of moles of H3PO4 / Volume of the solution (in liters)
Volume of the solution = 400 mL / 1000 (to convert mL to L)
Concentration (mol/L) ≈ 2.91 mol / 0.4 L
Concentration (mol/L) ≈ 7.28 mol/L
Therefore, the concentration of the solution is approximately 7.28 mol/L.