An aqueous KNO3 solution is made using 82.7 grams of KNO3, diluted to a total solution volume of 1.50 L. The density of this solution is 1.05 g/mL. What is the molality of this solution?
moles KNO3 = grams/molar mass
Solve for moles.
mass soln = volume x density = ??
mass H2O = total mass soln - mass solute.
molality = moles/kg solvent
so correct me if i may be wrong...
82.7gKNO3x1mol/101.11gKNO3=0.8179mol
1.5Lx1000ml/1Lx1.05g/1mL=1575g
1575-82.7=1492.3g
0.8179mol/1.4923kg=0.54808molal?
I agree but you have too many significant figures. You're allowed only 3.
To calculate the molality of a solution, we need to know the moles of solute dissolved in a certain mass of solvent. In this case, the solute is KNO3 and the solvent is water.
Let's break down the problem step by step:
Step 1: Calculate the mass of the solution.
The density of the solution is given as 1.05 g/mL, and the volume is 1.50 L. We can calculate the mass using the formula: mass = density × volume.
mass = 1.05 g/mL × 1500 mL = 1575 g
Step 2: Calculate the moles of KNO3.
To find the moles of solute, we need to divide the mass of KNO3 by its molar mass. The molar mass of KNO3 can be calculated by adding the atomic masses of potassium (K), nitrogen (N), and three oxygen (O) atoms.
molar mass of KNO3 = (atomic mass of K) + (atomic mass of N) + 3 × (atomic mass of O)
molar mass of KNO3 = 39.10 g/mol + 14.01 g/mol + 3 × 16.00 g/mol
molar mass of KNO3 = 101.10 g/mol
Now we can calculate the moles of KNO3 using the formula: moles = mass / molar mass.
moles of KNO3 = 82.7 g / 101.10 g/mol ≈ 0.818 mol
Step 3: Calculate the molality.
Molality is defined as the number of moles of solute dissolved in 1 kilogram (1000 grams) of solvent. In this case, the solvent is water.
molality = moles of solute / mass of solvent (in kg)
The mass of solvent in kg can be calculated by converting the mass of the solution in grams to kilograms.
mass of solvent = mass of solution - mass of solute
mass of solvent = 1575 g - 82.7 g = 1492.3 g = 1.4923 kg
Now we can calculate the molality:
molality = 0.818 mol / 1.4923 kg ≈ 0.548 mol/kg
Therefore, the molality of the aqueous KNO3 solution is approximately 0.548 mol/kg.