What is the molality of a solution formed by dissolving 1.95 mol of KCl in 17.0 mol of water (MM of water = 18.02 g/mol), answer in 3 sigfigs?
m = mols/kg solvent
m = 1.95/(18.02*17.0)
To find the molality of a solution, you need to divide the moles of solute (KCl) by the mass of the solvent (water) in kilograms.
First, let's calculate the mass of water using its molar mass and moles:
Mass of water = moles of water × molar mass of water
Mass of water = 17.0 mol × 18.02 g/mol
Now, we need to convert the mass of water from grams to kilograms:
Mass of water = 17.0 mol × 18.02 g/mol ÷ 1000 g/kg
Next, let's calculate the molality of the solution:
Molality = moles of solute (KCl) ÷ mass of solvent (water)
Molality = 1.95 mol ÷ (17.0 mol × 18.02 g/mol ÷ 1000 g/kg)
Calculating the value:
Molality = 1.95 mol ÷ (17.0 mol × 18.02 g/mol ÷ 1000 g/kg) = 0.0615 mol/kg
Rounded to 3 significant figures, the molality of the solution is 0.062 mol/kg.
To find the molality of a solution, you need to divide the moles of the solute by the mass of the solvent, and then multiply it by 1000 to convert it to units of mol/kg.
The formula for molality is:
molality = (moles of solute) / (mass of solvent in kg)
First, let's calculate the mass of water in the solution:
mass of water = number of moles of water × molar mass of water
mass of water = 17.0 mol × 18.02 g/mol
mass of water = 306.34 g
Next, convert the mass of water from grams to kilograms:
mass of water in kg = mass of water / 1000
mass of water in kg = 306.34 g / 1000
mass of water in kg = 0.30634 kg
Now, we can calculate the molality of the solution:
molality = moles of solute / mass of solvent in kg
molality = 1.95 mol / 0.30634 kg
molality ≈ 6.37 mol/kg
To match the number of significant figures given in the question (3 sigfigs), the molality is approximately 6.37 mol/kg.