Calculate the mass of urea required in making 2.5kg of 0.25 molar aqueous solution? which formula should I use mass by volume percentage or molality.help me out plz
0.25 M = 0.25 mols urea/L of solution by definition.
You don't give the density of the solution so I don't know where to begin. If you assume the density of the solution is 1.00 g/mL, which isn't true, then you want to make 2.5 L of solution.
0.25 M = ?mols/2.5 L
?mols = 0.25 x 2.5 = ?
Convert mols to grams urea by grams urea = mols urea x molar mass urea.
To calculate the mass of urea required to make a 0.25 molar aqueous solution, you need to use the molality formula. Molality is a concentration measure that relates the number of moles of solute to the mass of the solvent in kilograms.
The formula to calculate molality (m) is:
m = moles of solute / mass of solvent (in kg)
First, let's find the moles of solute required for a 0.25 molar solution:
Molarity (M) = moles of solute / volume of solution (in liters)
Rearranging the formula, moles of solute = Molarity × volume of solution.
Given that the molarity is 0.25 M and the volume of the solution is 2.5 kg, we can calculate the moles of solute:
moles of solute = 0.25 M × 2.5 L = 0.625 moles
Now, to calculate the mass of urea required, we need to know the molar mass of urea. The molar mass of urea (NH2CONH2) is approximately 60.06 g/mol.
mass of urea = moles of solute × molar mass of urea
mass of urea = 0.625 moles × 60.06 g/mol = 37.54 grams
Therefore, you would need approximately 37.54 grams of urea to make a 0.25 molar aqueous solution with a volume of 2.5 liters.
Note: In this case, we used the molality formula because the question asked for a molar concentration (0.25 M). If the question had asked for mass composition (mass by volume percentage), you would need to use a different formula.