Here's how to calculate the boiling point elevation of water when 4 moles of NaCl are added:

1. Understanding Boiling Point Elevation

Boiling point elevation is a colligative property, meaning it depends on the number of solute particles in a solution, not their identity. The more solute particles you add, the higher the boiling point will be.

2. Using the Formula

The formula for boiling point elevation is:

ΔT_b = i * K_b * m

Where:

* ΔT_b is the boiling point elevation (in °C)

* i is the van't Hoff factor (number of ions produced per formula unit of solute)

* K_b is the molal boiling point elevation constant for the solvent (for water, K_b = 0.512 °C/m)

* m is the molality of the solution (moles of solute per kilogram of solvent)

3. Calculating the van't Hoff Factor (i)

NaCl dissociates into two ions in water: Na⁺ and Cl^-. Therefore, i = 2.

4. Calculating Molality (m)

* You have 4 moles of NaCl.

* You have 1 kg of water.

* Molality (m) = 4 moles / 1 kg = 4 mol/kg

5. Calculating Boiling Point Elevation (ΔT_b)

* ΔT_b = 2 * 0.512 °C/m * 4 mol/kg = 4.096 °C

6. Finding the New Boiling Point

* The normal boiling point of water is 100 °C.

* The new boiling point is 100 °C + 4.096 °C = 104.096 °C

Therefore, the boiling point of water would increase by approximately 4.1 °C if 4 moles of NaCl were added to 1 kg of water.