Calculate the molarity of a solution prepared by dissolving 16 g of urea,
NH2CONH2, in 39 g of H2O. The density of the solution is 1.3 g/mL.
I've tried this question so many times but I keep getting it wrong please help me
mols urea = grams/molar mass = 16/60.06 = 0.266 mols.
M = mols/L soln
mass solution is 16g + 39 g = 55g
volume = mass/density = 55/1.3 = about 42.3 cc
M = 0.266/0.0423 = about 6.3M
I rounded here and there. You should go through it and do it more accurately.
To calculate the molarity of a solution, you need to know the number of moles of solute and the volume of the solution.
Step 1: Calculate the number of moles of urea:
First, convert the mass of the urea from grams to moles. The molar mass of urea is 60.06 g/mol.
Number of moles of urea = mass of urea / molar mass of urea
= 16 g / 60.06 g/mol
Step 2: Calculate the volume of the solution:
The density of the solution is given as 1.3 g/mL. Since the density is in grams per milliliter, you can convert the mass of the solution to volume using the formula:
Volume of the solution = mass of the solution / density of the solution
= 39 g / 1.3 g/mL
Step 3: Calculate the molarity of the solution:
The molarity (M) of a solution is defined as moles of solute per liter of solution.
Molarity of the solution = moles of urea / volume of the solution
= (16 g / 60.06 g/mol) / (39 g / 1.3 g/mL)
Now, let's do the calculations:
Number of moles of urea = 16 g / 60.06 g/mol ≈ 0.266 mol
Volume of the solution = 39 g / 1.3 g/mL ≈ 30 mL = 0.03 L
Molarity of the solution = 0.266 mol / 0.03 L ≈ 8.87 M
Therefore, the molarity of the solution prepared by dissolving 16 g of urea in 39 g of H2O is approximately 8.87 M.