Phosphoric Acid is usually obtained at an 85% phosphoric acid solution, by mass. If this solution is 15 M, what is the density of the solution? What is its MOLALITY?
Assume 1000 grams of solution.
then you have 850 grams phosphoric acid, and 150 grams of water.
15M=850/molmassH3PO4 / volumeinL
solve for volume, = 850/(molmass*15), figure molmass, then calculate volume.
finally, density= masssoluton/volumeL=
= 1000g/volumeL figured above
you may want to change that to g/ml
density x 1000 mL x %H3PO4 x (1/molar mass) = 15M
Solve for density = approximately 1.7 but you need to do it more accurately.
mass of 1000 mL = 1.73 x 1000 mL = 1730 g
mass H3PO4 = 1730 x 0.85 = 1470g
g solvent = 1730g-1470 = 260g
m = mols solute/kg solvent/kg solvent = 15/0.260 = about 57m.
To find the density of the solution, we can use the formula:
Density = (mass of solution) / (volume of solution)
Since we know that the solution is 85% phosphoric acid by mass, we can assume that the mass of the solution is 85 grams (g) for every 100 milliliters (mL) of solution.
Now we need to calculate the volume of the solution. The molarity (M) of the solution is given as 15 M, which means it contains 15 moles (mol) of phosphoric acid in 1 liter (L) of solution.
To calculate the volume, we can use the formula:
Volume = (number of moles) / (molarity)
Volume = 15 mol / 15 M = 1 L
Now we can calculate the density:
Density = (mass of solution) / (volume of solution)
Density = 85 g / 1000 mL = 0.085 g/mL
Therefore, the density of the solution is 0.085 g/mL.
To calculate the molality, we need to use the formula:
Molality = (number of moles of solute) / (mass of solvent in kg)
In this case, the solute is phosphoric acid, which has 15 moles, and the solvent is the solution (water). However, we need to calculate the mass of the water.
Since the mass of the phosphoric acid solution is 85 g, and assuming the density of the water is 1 g/mL, we can calculate the mass of the water as:
Mass of water = Mass of solution - Mass of phosphoric acid = 85 g - 85 g = 0 g
Since the mass of the water is zero, the molality of the solution is not defined (undefined).
Therefore, the molality of the solution is undefined.
To determine the density and molality of the 85% phosphoric acid solution, we need to use the known concentration and information about the density of the pure compound.
1. Finding the density:
The density of the solution can be calculated by using the mass percent and the known density of pure phosphoric acid. The equation for density (D) is:
D = (mass of solute) / (volume of solution)
Given that the solution is 85% phosphoric acid by mass, we can assume that 100 g of the solution contains 85 g of phosphoric acid. Let's assume the solution has a total volume of 100 mL.
Mass of phosphoric acid = 85 g
Mass of solution = 100 g
Volume of solution = 100 mL = 0.1 L (since 1 L = 1000 mL)
Now, using the density equation:
D = (85 g) / (0.1 L)
Calculating the density, we find that the solution has a density of 850 g/L.
2. Finding the molality:
Molality (m) is defined as the number of moles of solute per kilogram of solvent. To find the molality, we need to know the number of moles of phosphoric acid and the mass of the solvent.
Given that the solution is 15 M, it means that there are 15 moles of phosphoric acid in 1 liter of solution. Since the density of the solution is 850 g/L, we can assume that 1 kg of the solution is equal to 850 g.
To find the number of moles of phosphoric acid in the solution, we need to convert the volume to liters:
Volume of solution = 0.1 L
Number of moles of phosphoric acid = Volume of solution (in liters) * Molarity
Number of moles = 0.1 L * 15 mol/L
Calculating the number of moles, we find that there are 1.5 moles of phosphoric acid in the solution.
Now, to calculate the molality:
m = (number of moles of solute) / (mass of solvent in kg)
We are assuming that the solvent is water, and since the mass of the solution is 100 g (0.1 kg), we can use this as the mass of the solvent.
m = 1.5 moles / 0.1 kg
Calculating the molality, we find that the solution has a molality of 15 mol/kg.
Therefore, the density of the 85% phosphoric acid solution is 850 g/L, and its molality is 15 mol/kg.