How much would the freezing point of the water decrease if 4 mol of NaCl were added to 1 kg of water for water and i 2 for NaCl?

The freezing point depression can be calculated using the formula: ΔTf = i * Kf * m, where i is the van't Hoff factor (number of particles), Kf is the cryoscopic constant, and m is the molality of the solution. Given that i for NaCl is 2, and assuming Kf for water is 1.86 °C/kg/mol, the ΔTf for a 4 mol NaCl solution in 1 kg of water can be calculated.