How does the vapor pressure over a concave liquid surface compare to a flat surface______________________?
Show answer Hide answer
Answer: A. less man the vapour pressure over the plane surface
Explanation
According to the Kelvin equation, the vapor pressure over a concave liquid surface is lower. Surface curvature creates a pressure deficit that reduces the escaping tendency of liquid molecules. Consequently, concave menisci maintain a lower equilibrium vapor pressure than flat plane surfaces. The Kelvin equation relates vapor pressure changes to the curvature radius of liquid-gas interfaces. Concave surfaces feature negative curvature radii, which decrease chemical potential and evaporation rates. Capillary condensation in narrow pores is governed directly by this fundamental thermodynamic principle.
Porous catalyst structures and soils use Kelvin effects to explain moisture condensation inside tiny pores. Atmospheric cloud physics incorporates surface curvature effects when studying microscopic droplet formation dynamics. Chemical engineers account for vapor pressure depressions when analyzing gas absorption in packed towers. Option B incorrectly assumes surface curvature has no thermodynamic impact on local vapor pressures. Option C describes convex surfaces like droplets, which actually exhibit higher vapor pressures than flat planes. Option D implies zero vapor pressure, which only occurs at absolute zero temperature or hard vacuums.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. What are known as the three “Ts” essential for complete combustion____________________?
Show answer Hide answer
Answer: A. temperature, time, and turbulance
Sufficient temperature ensures the fuel-air mixture reaches its required ignition point instantly. Adequate time allows chemical combustion reactions to proceed completely to carbon dioxide and water. Turbulence promotes...
Q2. What is the mass density value in kgsecVm4 for water at 0°C_________________?
Show answer Hide answer
Answer: D. 101.9
Mass density in gravitational or engineering units is expressed in kilograms force-second squared per meter to the fourth power. This value is derived by dividing the standard mass density of water by the local accelerat...
Q3. What elemental composition is typical for standard soldering alloys__________________?
Show answer Hide answer
Answer: A. tin, lead and small percentage of antimony
Standard soft solders are primarily binary alloys of tin and lead containing small percentages of antimony. Adding antimony enhances the mechanical strength and creep resistance of the solid soldered joint. This specific...
Q4. Under what polytropic index value (n) is the work done per unit mass during air compression minimized______________?
Show answer Hide answer
Answer: A. 1
An isothermal compression process maintains constant temperature with a polytropic index of one. Work done during gas compression is directly proportional to the area under the process curve. Isothermal compression requi...
Q5. How does the thermal efficiency of a crankcase-scavenged two-stroke petrol engine compare to a four-stroke engine with an equal compression ratio_____________________?
Show answer Hide answer
Answer: B. lower
Crankcase-scavenged two-stroke petrol engines use the crankcase to compress the incoming air-fuel charge before transfer. This method results in poor scavenging efficiency, allowing fresh mixture to escape directly into...
Q6. How are the internal water tubes arranged in a Babcock and Wilcox boiler__________________?
Show answer Hide answer
Answer: C. inclined
A Babcock and Wilcox boiler is a classic water tube boiler featuring an arrangement of inclined water tubes. These straight water tubes connect front and rear headers to promote natural convective water circulation loops...