Answer :
Final answer:
To determine the expected boiling point of a KCl solution, calculate the molality, then apply the boiling point elevation constant. For a solution with 128 g of KCl in 1.3 kg of water, the expected boiling point would be approximately 101.3463°C after accounting for the dissociation of KCl into ions.
Explanation:
Boiling Point Elevation Calculation
To find the expected boiling point of a solution of KCl dissolved in water, first we need to calculate the molality of the solution using the given mass of KCl and the molar mass of KCl. Then we can use the boiling point elevation constant (Kb) to determine the boiling point elevation.
The molality (m) is found using the formula:
m = moles of solute / kilograms of solvent
Moles of KCl = 128 g / 74.55 g/mol
= 1.7169 moles
Molality of KCl solution = 1.7169 moles / 1.3 kg
= 1.3207 m
Since KCl is a strong electrolyte, it will dissociate into K+ and Cl- ions. We must account for both ions in the boiling point elevation calculation:
Total moles of ions = 1.7169 moles of K+ + 1.7169 moles of Cl-
= 3.4338 moles
Boiling point elevation (ΔTb) = i * Kb * m
Where i is the van't Hoff factor (i = 2 for KCl), Kb is the ebullioscopic constant, and m is the molality.
ΔTb = 2 * 0.51°C/m * 1.3207 m
= 1.3463°C
The normal boiling point of water is 100°C, so the expected boiling point of the KCl solution would be:
Boiling point = 100°C + 1.3463°C
= 101.3463°C
