What is the mass percent of an aqueous sodium hydroxide solution in which the molality of NaOH is 6.25m? The density of the solution is 1.2219 g/mL
Do you have a 6.25m or a 6.25M solution? Mathmate's answer and definition is for 6.25M.
The correct answer for 6.25m is below.
m is molality and the problem states molality (not molarity).
molality = mols solute/kg solvent.
6.25m means 6.25 mols NaOH/kg solvent.
g = mols x molar mass = 6.25 x 40 = about 250; therefore, you have a solution of 250g NaOH in (1000 + 250) or 250 g NaOH in 1250 g solution.
mass% = (250/1250)*100 = ?about 20%
Thank you Dr. Bob.
To find the mass percent of a solute in a solution, we need to know the mass of the solute and the mass of the solution.
To calculate the mass of the solute (NaOH) in the solution, we can use the formula:
Mass of solute (NaOH) = molality × molar mass of solute × mass of solvent (water)
First, let's calculate the mass of solute (NaOH):
Given:
Molality of NaOH (m) = 6.25 m
Molar mass of NaOH = 22.99 g/mol + 16.00 g/mol + 1.01 g/mol = 40.00 g/mol (rounded to two decimal places)
Now, we can calculate the mass of solute (NaOH):
Mass of solute (NaOH) = 6.25 m × 40.00 g/mol × mass of solvent (water)
To find the mass of the solvent (water), we need to know the volume and density of the solution.
Given:
Density of the solution = 1.2219 g/mL
Let's assume that we have 1000 mL (or 1 L) of the solution to make this calculation easier.
Mass of solvent (water) = volume of solution × density of solution
Mass of solvent (water) = 1000 mL × 1.2219 g/mL = 1221.9 g (rounded to two decimal places)
Now, let's substitute the value of the mass of solvent (water) into the formula for the mass of solute (NaOH):
Mass of solute (NaOH) = 6.25 m × 40.00 g/mol × 1221.9 g
We can now calculate the mass of solute (NaOH).
Next, to find the mass percent of the solute in the solution, we use the formula:
Mass percent = (mass of solute / mass of solution) × 100
The mass of the solution is the sum of the mass of solute (NaOH) and the mass of solvent (water).
Mass of solution = mass of solute (NaOH) + mass of solvent (water)
Finally, plug the values into the formula for mass percent to get the answer.
molarity is the number of moles per unit volume (L).
6.25 m means 6.25 moles per L of solution, or per 1221.9 g of solution.
Calculate the mass density accordingly.