What colligative properties are displayed by these situations.
1. Antifreeze is added to car cooling system preventing freezing when air temp is below 0 degrees C.
2. Ice melts on sidewalk after salt has been spread
Ethylene glycol is permanent antifreeze that is added to cars these days. That lowers the freezing point and raises the boiling point AND most cars these days operate with the radiator under pressur which raises the boiling point even higher. The engine is a little more efficient at the higher temperature.
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Both are freezing point depression.
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So the antifreeze one doesn't have anything to do with vapor pressure?
1. The colligative property displayed in this situation is freezing point depression. When antifreeze is added to the car cooling system, it lowers the freezing point of the coolant. This means that the coolant can withstand lower temperatures without freezing, allowing the car to start and run even when the air temperature is below 0 degrees Celsius.
To understand how to lower the freezing point, we can look at the concept of colligative properties. Colligative properties are properties of a solution that depend on the number of particles (such as molecules or ions) in the solution, regardless of their identity. This means that the effect of the particles is additive, and the more particles present, the greater the effect.
In this case, antifreeze molecules (such as ethylene glycol) are added to the water in the car cooling system. These molecules disrupt the formation of ice crystals by getting in between the water molecules and preventing them from organizing into a solid structure. This requires energy, so the freezing point of the solution decreases.
To calculate the freezing point depression, you can use the equation:
ΔT = Kf × m × i
- ΔT is the change in freezing point (in this case, it is the difference between 0 degrees Celsius and the new freezing point).
- Kf is the cryoscopic constant, which is specific to the solvent (in this case, water).
- m is the molality of the solute, which represents the amount of solute in moles per kilogram of solvent.
- i is the van't Hoff factor, which represents the number of particles that each formula unit of solute dissociates into (in this case, ethylene glycol does not dissociate, so i would be 1).
2. The colligative property displayed in this situation is boiling point elevation. When salt (such as sodium chloride) is spread on the sidewalk and reacts with the ice, it lowers the freezing point of the ice. As a result, the ice melts and forms a liquid layer on top of the sidewalk.
Similar to the freezing point depression, the boiling point elevation is a colligative property that depends on the number of solute particles in a solution. In this case, the dissolved salt particles increase the boiling point of the solution.
To calculate the boiling point elevation, you can use the equation:
ΔT = Kb × m × i
- ΔT is the change in boiling point (in this case, it is the difference between the boiling point of pure water and the boiling point of the solution).
- Kb is the ebullioscopic constant, which is specific to the solvent (in this case, water).
- m is the molality of the solute, representing the amount of solute in moles per kilogram of solvent.
- i is the van't Hoff factor, representing the number of particles that each formula unit of solute dissociates into (in this case, sodium chloride dissociates into two ions, so i would be 2).
Keep in mind that the actual values of Kf, Kb, and i will depend on the specific solvent and solute being used, so it is important to use the correct values for accurate calculations.