Technician A says that vapor has a fixed volume that remains the same when temperature increases. Technician B says that decreasing the temperature on a vapor will increase the pressure. Who is correct?
A. Both Technician A and Technician B
B. Technician A
C. Technician B
D. Neither Technician A nor B
The Correct Answer and Explanation is :
The correct answer is D. Neither Technician A nor Technician B.
Explanation:
Technician A’s statement that vapor has a fixed volume that remains the same when temperature increases is incorrect. Gases (including vapors) do not have a fixed volume; they expand to fill the container they are in. According to the Ideal Gas Law, which states ( PV = nRT ), where ( P ) is pressure, ( V ) is volume, ( n ) is the number of moles, ( R ) is the gas constant, and ( T ) is temperature in Kelvin, any increase in temperature (assuming a constant number of moles and pressure) would lead to an increase in volume if the gas is allowed to expand. Thus, vapor will occupy a larger volume if heated in an unconfined space.
Technician B’s assertion that decreasing the temperature on a vapor will increase the pressure is also incorrect. When the temperature of a gas decreases, its kinetic energy reduces, leading to fewer and less energetic collisions of gas molecules with the walls of the container, which results in a decrease in pressure, provided the volume of the gas remains constant. This relationship is explained by Gay-Lussac’s Law, which states that the pressure of a gas is directly proportional to its temperature (in Kelvin) when the volume is held constant.
In summary, both technicians have misunderstood the behavior of vapors and gases in relation to temperature and pressure. Vapors do not have a fixed volume, and decreasing temperature leads to a decrease in pressure rather than an increase. Understanding the principles of gas behavior is crucial in various applications, including engineering and thermodynamics, where precise control over temperature and pressure is essential.