Question

KCl is an ionic salt with a formula weight of 74.54 g/mole.

A 1.417 M (mole/liter) KCl solution has a density of 1064.5 grams/liter at 20 OC.
Use the Molarity and the formula weight to find the mass (g) of salt in one liter.
Then, find the mass (g and kg) of water in one liter of the solution.
Determine the molality (m), or moles of salt per kg of water, by dividing the moles of salt in one liter by the kg of water in one liter.
Show all units and use proper significant figures

Answer 1

mass of water = 958 g = 0.958 kg

m = 1.48 mol/kg

Step-by-step explanation:

Given:

MM(KCl)= 74.54 g/mol

M= 1.417 mol/L

density of solution= 1064 g/L

To calculate the mass of water in 1 L of solution, first we have to multiply the molarity of the solution (M) by the molecular weight of KCl (MM):

1.417 mol/L x 74.54 g/mol = 105.62 g/L

As the density of the solution is 1064 g/L, we know that 1 L is equal to 1064 g. So, we have 105.62 g of KCl in 1064 g of solution. The mass of water will be the difference between the mass of solution and the mass of solute:

mass of water (g) = 1064 g - 105.6 g = 958.4 g

mass of water (kg)= 958.4 g x 1 kg/1000 g = 0.958 kg

To determine the molality (m):

m = moles of KCl/kg water

m = 1.417 moles/0.958 kg = 1.479 mol/kg