Find the Mass of Air in the Room and the Air's Weight

In summary, the conversation discusses determining the mass and weight of air in a room based on its temperature, pressure, and dimensions. The conversation also mentions the conversion of °F to °R and the calculation of density using the ideal gas law. The individual asking the question is questioning the validity of their calculated density due to a discrepancy in units.
  • #1
Northbysouth
249
2

Homework Statement



The air in a room measuring 8 ft x 9 ft x 12 ft is at 80°F and 1 atm. Determine the mass of the air, in lb, and its weight, in lbf, if g = 32.0 ft/s2

Homework Equations


1 °F = 460.86°R

dair = mair/vair


The Attempt at a Solution



The air has the same mass as the room, thus mair = 8x9x12

mair = 864 ft3

dair = mair/vair

dair = ρ/RT

dair = 1 atm/(53.35 ft lb/lbm °R)(540.67°R)

dair = 3.4668x10-5 atm lbm/ft lbf

My density seems kinda low. What am I missing? Is it the gc?
 
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  • #2
You should check your units, especially for R.

A density unit of atm lbm/ ft-lbf makes no sense.
 
  • #3
Wrong question.
 
Last edited:

1. What is the mass of air in the room?

The mass of air in a room depends on the volume of the room and the density of the air. To find the mass, you can use the formula: mass = density x volume. The density of air is approximately 1.2 kg/m^3, so to find the mass in kilograms, you would multiply the density by the volume in cubic meters.

2. How do you measure the volume of the room?

The volume of a room can be measured by multiplying the length, width, and height of the room. If the shape of the room is irregular, you can use a tool such as a laser measurer or a measuring tape to get accurate measurements.

3. How do you determine the density of air?

The density of air can be determined by using the ideal gas law, which states that density = (pressure x molar mass) / (gas constant x temperature). You can also find the density of air by looking it up in a reference table or using a density calculator.

4. Why is it important to find the mass of air in a room?

Knowing the mass of air in a room can help in various scientific experiments and calculations. It can also be useful in engineering and construction projects, as the weight of air can affect the structural integrity of a building. Additionally, understanding the mass of air can provide insights into air quality and ventilation systems.

5. How does the mass of air affect the weight of objects in the room?

The mass of air in a room has a negligible effect on the weight of objects in the room. This is because air has a very low density compared to other objects in the room, such as furniture and people. However, in high-altitude areas where air density is lower, the weight of objects may be slightly different compared to at sea level due to the difference in air density.

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