Chem #3

What is the definition of surface tension?

• Surface tension is the pressure exerted by a gas above a liquid.

• Surface tension is the weight of a liquid that determines its flow rate.

• Surface tension is the temperature at which a liquid boils.

• Surface tension is the force that causes the surface of a liquid to contract and resist external force, due to cohesive interactions among liquid molecules.

How does temperature affect the vapor pressure of a liquid?

• Temperature has no effect on vapor pressure.

• Higher temperatures decrease vapor pressure.

• Vapor pressure is constant regardless of temperature.

• Temperature increases vapor pressure of a liquid.

What is boiling point elevation and how is it calculated?

• Boiling point elevation refers to the temperature at which a liquid turns into gas without any solute.

• Boiling point elevation is the increase in boiling point due to the addition of a solute, calculated using ΔT_b = i * K_b * m.

• Boiling point elevation is the decrease in boiling point due to the addition of a solute.

• Boiling point elevation is calculated using ΔT_b = K_b / m.

Define molar heat of vaporization.

• The molar heat of vaporization is the energy needed to vaporize one mole of a substance at its boiling point.

• The molar heat of vaporization is the energy needed to condense one mole of a substance at its boiling point.

• The molar heat of vaporization is the temperature at which a substance boils.

• The molar heat of vaporization is the energy required to freeze one mole of a substance.

What role does intermolecular force play in surface tension?

• Surface tension is solely caused by gravitational forces acting on the liquid.

• Intermolecular forces repel surface molecules, reducing surface tension.

• Intermolecular forces have no effect on the behavior of surface molecules.

• Intermolecular forces create attractive interactions that lead to surface tension by pulling surface molecules inward.

How does the presence of solutes affect vapor pressure?

• The presence of solutes increases vapor pressure.

• The presence of solutes stabilizes vapor pressure.

• Solutes have no effect on vapor pressure.

• The presence of solutes decreases vapor pressure.

Explain the concept of boiling point in relation to atmospheric pressure.

• The boiling point is the temperature at which a solid turns into a gas.

• The boiling point is the temperature at which a liquid freezes.

• The boiling point is the temperature at which a liquid's vapor pressure equals atmospheric pressure.

• The boiling point is always the same regardless of pressure.

What is the significance of molar heat of vaporization in phase changes?

• It measures the temperature at which a substance freezes.

• It indicates the density of a liquid at various temperatures.

• It quantifies the energy required for a substance to change from liquid to gas, affecting boiling points and evaporation.

• It describes the color change during a phase transition.

Compare the vapor pressures of water and ethanol at room temperature.

• Ethanol has a higher vapor pressure than water at room temperature.

• Ethanol has a lower vapor pressure than water at room temperature.

• Both water and ethanol have the same vapor pressure at room temperature.

• Water has a higher vapor pressure than ethanol at room temperature.

How does surface area influence surface tension?

• A larger surface area decreases the overall surface tension.

• Surface area influences the total effect of surface tension but not the surface tension coefficient itself.

• Surface area has no effect on surface tension whatsoever.

• Surface area directly increases the surface tension coefficient.