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

• Northbysouth
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.
Northbysouth

## 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

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?

You should check your units, especially for R.

A density unit of atm lbm/ ft-lbf makes no sense.

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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