Boiling Point of Water and Atmospheric Pressure

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Questions and Answers

What is defined as the normal boiling point of a liquid?

The temperature at which a liquid can no longer exist

The temperature at which a liquid turns completely into vapour

The temperature at which a liquid can exist as a solid

The temperature at which the liquid and vapours are in equilibrium at one atmospheric pressure (correct)

How does altitude affect the boiling point of water?

It decreases the boiling point (correct)

It causes the boiling point to remain the same

It causes the boiling point to fluctuate

It increases the boiling point

In a closed vessel with solid iodine, what happens over time?

Solid iodine solely transforms into iodine vapour

The colour intensity of the vapour decreases continuously

Equilibrium is reached when iodine vapour fills the vessel (correct)

Iodine vapour solidifies back into solid iodine

Which of the following substances undergo sublimation?

Iodine Signup and view all the answers

Which statement about boiling points is true?

Boiling points vary based on environmental pressure Signup and view all the answers

What is a common characteristic of solid-vapour equilibrium?

Both solid and vapour phases are interchanging continuously Signup and view all the answers

At what temperature does water boil at one atmospheric pressure?

100°C Signup and view all the answers

What is a saturated solution?

A solution where the solute concentration remains constant at a given temperature. Signup and view all the answers

What occurs in a saturated solution at dynamic equilibrium?

The rates of dissolution and crystallization are equal. Signup and view all the answers

What happens to carbon dioxide when a soda water bottle is opened?

Carbon dioxide rapidly escapes due to decreased pressure. Signup and view all the answers

Which factor does NOT affect the concentration of solute in a saturated solution?

Size of the solute particles. Signup and view all the answers

How was the dynamic nature of equilibrium confirmed in the case of sugar dissolution?

Using radioactive sugar to track exchange between phases. Signup and view all the answers

What happens to the concentration of a gas in liquid as pressure increases?

It increases. Signup and view all the answers

What is a characteristic of the equilibrium for solid-liquid systems?

There is only one temperature at 1 atm where phases can coexist. Signup and view all the answers

When a sealed soda water bottle is opened, what occurs to the dissolved carbon dioxide gas?

It escapes to form a new equilibrium. Signup and view all the answers

At a given temperature, what can be said about the vapor pressure in liquid-vapor equilibrium?

It is constant. Signup and view all the answers

How does the solubility of solids in liquids change with temperature?

It is constant at a given temperature. Signup and view all the answers

Study Notes

Liquid-Vapour Equilibrium

Water and water vapour reach equilibrium at 1.013 bar and 100°C in a closed vessel.
The boiling point of water at 1.013 bar is 100°C.
For pure liquids, the temperature at which the liquid and vapour coexist at equilibrium under 1.013 bar pressure is known as the normal boiling point.
Boiling point varies with atmospheric pressure; it decreases at higher altitudes due to lower pressure.

Solid-Vapour Equilibrium

When solids sublime, they transition directly to the vapour phase.
Placing solid iodine in a closed vessel produces violet vapour, the intensity of which increases over time until it stabilizes, indicating equilibrium.
The sublimation and condensation of iodine can be represented as:
I₂(solid) ⇌ I₂(vapour)
Other substances that exhibit solid-vapour equilibrium include:
- Camphor: Camphor (solid) ⇌ Camphor (vapour)
- Ammonium chloride (NH₄Cl): NH₄Cl (solid) ⇌ NH₄Cl (vapour)

Equilibrium in Dissolution

Solids in Liquids

Solubility of substances like salt or sugar in water is limited and varies with temperature.
A saturated solution occurs when no more solute can dissolve at a specific temperature.
Dynamic equilibrium exists between dissolved solute and undissolved solid, represented as:
- Sugar (solution) ⇌ Sugar (solid)
In saturated solutions, the rate of dissolution equals the rate of crystallization.
Radioactive sugar experiments demonstrate dynamic equilibrium; radioactivity transfers between solution and solid, reaching a constant ratio of molecules over time.

Gases in Liquids

The release of carbon dioxide from opened soda water illustrates changes in solubility due to pressure.
Equilibrium between gaseous CO2 and dissolved CO2 can be expressed as:
- CO2 (gas) ⇌ CO2 (in solution)
Henry's law dictates that the mass of gas dissolved is proportional to the gas pressure above the solvent, with higher temperatures decreasing solubility.
Sealed soda bottles maintain high gas solubility under pressure; opening the bottle allows gas to escape, transitioning to a lower pressure equilibrium, leading to flat soda.

General Observations on Physical Equilibria

Solid-Liquid Equilibrium: A single melting point exists at 1 atm pressure where solid and liquid phases coexist without heat exchange.
Liquid-Vapor Equilibrium: Vapor pressure remains constant at a given temperature.
Dissolution of Solids: Solubility remains constant at specific temperatures.
Dissolution of Gases: Gas concentration in liquid is directly proportional to the partial pressure of the gas over the liquid.

Summary of Key Processes

Liquid-Vapor: H2O (l) ⇌ H2O (g), vapor pressure constant at given temperature.
Solid-Liquid: H2O (s) ⇌ H2O (l), melting point fixed at constant pressure.
Solute in Solution: Sugar(s) ⇌ Sugar(solution), concentration constant at given temperature for solute in a solution.
Gas in Liquid: CO2(g) ⇌ CO2(aq), concentration ratios ([gas(aq)]/[gas(g)]) remain constant at given temperature.

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Description

This quiz explores the concepts of boiling points, specifically focusing on water and water vapor equilibrium at atmospheric pressure. It highlights how altitude affects the boiling point of liquids and the significance of the normal boiling point. Test your understanding of these fundamental principles in thermodynamics!