Question

A sample of HgCl₂ weighing 9.41 g is dissolved in 32.75 g of ethanol, C₂H₅OH (Kb = 1.20 °C/m). The boiling point elevation of the solution is 1.27 °C. Is HgCl₂ an electrolyte in ethanol? Show your calculations.

Answer 1

The calculation indicates that the van 't Hoff factor for HgCl₂ in ethanol is approximately 1, suggesting that HgCl₂ does not dissociate into ions and is not an electrolyte in ethanol.

Step-by-step explanation:

To determine whether HgCl₂ is an electrolyte in ethanol, we use the boiling point elevation formula ΔT = i*Kb*m, where ΔT is the boiling point elevation, i is the van 't Hoff factor (number of particles the compound dissociates into), Kb is the ebullioscopic constant of ethanol, and m is the molality of the solution.

First, calculate the molality of the solution: m = moles of solute / kg of solvent. The molar mass of HgCl₂ is approximately 271.5 g/mol, so moles of HgCl₂ = 9.41g / 271.5 g/mol = 0.03465 mol. The mass of ethanol is 32.75g, which is 0.03275 kg. Thus, molality (m) = 0.03465 mol / 0.03275 kg = 1.0579 m.

Now, use the boiling point elevation data: ΔT = 1.27°C = i * (1.20°C/m) * 1.0579 m. Solving for i gives i = ΔT / (Kb * m) = 1.27°C / (1.20°C/m * 1.0579 m). From this, i ≈ 1, which suggests that HgCl₂ does not ionize significantly in ethanol and is not an electrolyte since we expected i to be 1 for a non-electrolyte.