. A 100 g of ammonium chloride solution is 30 % by mass with a density of 1.024 g/mL. Calculate molarity and molality of a solution.
molarity = M = mols/L
molality = m = moles/kg solvent.
M first. In steps:
density = 1.024 g/mL; therefore, 1000 mL has a mass of 1.024 x 1000 = 1024 g.
How much of that is NH4Cl? That's 1024 g x 0.30 = 307.2 g NH4Cl
How many moles is that? That's 307.2 g x 1 mol/53.5 g = 5.74 moles.
Therefore, M = mols/L = ?
molality = m = moles/kg solvent. In steps:
You have moles NH4Cl from above as 5.74 moles NH4Cl.
Total mass of solution from above is 1024 g.
Total mass of NH4Cl from above is 307.2 g
mass solution - mass solute = mass solvent = 1024 - 307.2 = ?. Convert to kg. m = mols/kg solvent = ?
Post your work if you get stuck.
To calculate the molarity and molality of a solution, we need to first determine the number of moles of solute (in this case, ammonium chloride) present.
1. Calculate the mass of ammonium chloride in the solution:
Mass of ammonium chloride = mass of solution × mass percent
= 100 g × 30/100
= 30 g
2. Calculate the number of moles of ammonium chloride:
Number of moles = mass / molar mass
= 30 g / (14.01 g/mol + 1.01 g/mol + 35.45 g/mol)
= 30 g / 53.47 g/mol
≈ 0.561 mol
3. Calculate the molarity of the solution:
Molarity (M) = number of moles / volume of solution (in liters)
= 0.561 mol / (100 g / 1,000 g/L)
= 5.61 M
4. Calculate the molality of the solution:
Molality (m) = number of moles / mass of solvent (in kilograms)
= 0.561 mol / (100 g - 30 g) / 1,000 g/kg
= 7.48 m
Therefore, the molarity of the solution is 5.61 M, and the molality of the solution is 7.48 m.