Answer:
Step-by-step explanation:
First, we need to calculate the moles of KCl:
Calculate the molar mass of KCl:
KCl = 39.10 g/mol (atomic weight of K) + 35.45 g/mol (atomic weight of Cl)
= 74.55 g/mol
Calculate the moles of KCl:
moles of KCl = mass of KCl / molar mass of KCl
= 19.9 g / 74.55 g/mol
= 0.267 mol
Next, we need to convert the mass of the solvent (water) from milliliters to kilograms:
Convert mL to L:
750.0 mL = 750.0 mL * (1 L / 1000 mL)
= 0.7500 L
Calculate the mass of water:
mass of water = volume of water x density of water
= 0.7500 L x 1000 g/L
= 750.0 g
Convert the mass of water to kilograms:
mass of water = 750.0 g / 1000 g/kg
= 0.7500 kg
Now we can calculate the molality of the solution:
molality = moles of solute / mass of solvent (in kg)
molality = 0.267 mol / 0.7500 kg
= 0.356 mol/kg
Therefore, the molality of the solution is 0.356 mol/kg.