How does salt affect the boiling point of water?

How does salt affect the boiling point of water?

• A. Salt lowers the boiling point of water.
• B. Salt elevates the boiling point of the salt-water mixture.
• C. Salt has no effect on boiling point.
• D. Salt causes water to boil at room temperature.

Answer: (B)

When something is dissolved in water, the vapor pressure of the water becomes lower than that of pure water. Dissolved salt splits into ions, and these particles interfere with water molecules escaping into the vapor. Boiling happens when the vapor pressure of the liquid equals the surrounding atmospheric pressure, so you must heat the mixture a bit more to reach that point. This is boiling point elevation, a colligative property that grows with how much solute is present (and with the number of particles the solute creates). For table salt, dissociation yields roughly two particles, so the effect is noticeable but not huge. In short, salt makes the water boil at a higher temperature, not lower, and not at room temperature.

When something is dissolved in water, the vapor pressure of the water becomes lower than that of pure water. Dissolved salt splits into ions, and these particles interfere with water molecules escaping into the vapor. Boiling happens when the vapor pressure of the liquid equals the surrounding atmospheric pressure, so you must heat the mixture a bit more to reach that point. This is boiling point elevation, a colligative property that grows with how much solute is present (and with the number of particles the solute creates). For table salt, dissociation yields roughly two particles, so the effect is noticeable but not huge. In short, salt makes the water boil at a higher temperature, not lower, and not at room temperature.