Sure! I'd be happy to help you solve these problems.
(a) To find the molality of chloride ions in an aqueous solution of iron(III) chloride, we need to determine the moles of chloride ions and the mass of water.
Given:
- xFeCl3 = 0.0195 (moles of iron(III) chloride)
- We need the molality of chloride ions, so we need to find the moles of chloride ions.
In one mole of iron(III) chloride (FeCl3), there are three moles of chloride ions (Cl-). Therefore, the moles of Cl- in the solution would be 3 times the value of xFeCl3.
So, the moles of chloride ions (mol Cl-) = 3 * xFeCl3
Now, we need to find the mass of water (kg solvent) in the solution. Since the problem doesn't provide the mass directly, we need other information to calculate it.
(b) To find the molality of hydroxide ions in a solution of barium hydroxide, we need to determine the moles of hydroxide ions and the mass of water.
Given:
- Mass of barium hydroxide (Ba(OH)2) = 9.16 g
- Mass of water = 179 g
- We need the molality of hydroxide ions, so we need to find the moles of hydroxide ions.
First, we need to convert the mass of barium hydroxide to moles. To do this, divide the given mass by the molar mass of barium hydroxide.
Molar mass of Ba(OH)2 = atomic mass of Ba + 2*(atomic mass of O) + 2*(atomic mass of H)
After finding the moles of Ba(OH)2, multiply it by 2 to get the moles of hydroxide ions because there are two moles of OH- per mole of Ba(OH)2.
Now, we need to find the mass of water (kg solvent) in the solution. Since the problem provides the mass of water directly, you can use that value.
(c) To find the molality of an ammonia solution with a given molarity and density, we need to determine the moles of ammonia and the mass of water.
Given:
- Molarity of NH3(aq) = 12.70 M
- Density of NH3(aq) = 0.9519 g·cm-3
- We need the molality of the solution, so we need to find the moles of ammonia.
First, convert the given concentration from moles per liter (Molarity, M) to moles per kilogram (molality, m) using the density of the solution.
Moles of NH3 = Molarity * Volume of solution (in liters)
To find the volume of the solution, divide the mass of the solution by its density.
Volume of solution = Mass of solution / Density of solution
Finally, to determine the overall mass of the solution (kg solvent), subtract the mass of NH3 from the mass of the solution.
Mass of water (kg solvent) = Mass of solution - Mass of NH3
Now, use the moles of NH3 and the mass of water to calculate the molality using the formula:
molality (m) = moles of NH3 / mass of water
I hope this explanation helps you understand how to solve these problems. Let me know if you have any further questions!