Why multiply atm by atmospheric pressure in pascals?

In summary: And since the given values are in liters, the final answer needs to be divided by 1000 to convert from milliliters to liters. This results in the final answer being in joules, the unit of energy.
  • #1
gibson101
47
0
Consider the following two-step process. Heat is allowed to flowout of an ideal gas at constant volume so that its pressure dropsfrom PA = 2.7 atmto 1.4 atm. Then the gas expands at constant pressure, from avolume of 6.8 L to VC = 13.1 L where the temperature reaches its originalvalue. See Fig. 15-27.

In the following work, why is 1.4 atm multiplied by 1.013e5 pascals? And to clarify, PA=2.7 just means pressure A.
Figure 15-27
(a) Calculate the total work done by the gas in the process (in joules).
Work done by gas along the parts BC W2= PdV
= P( Vc-Vb)

= 1.4*1.013*105( 13.1-6.8)*10-3
=893.466J
 
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  • #2
gibson101 said:
Consider the following two-step process. Heat is allowed to flowout of an ideal gas at constant volume so that its pressure dropsfrom PA = 2.7 atmto 1.4 atm. Then the gas expands at constant pressure, from avolume of 6.8 L to VC = 13.1 L where the temperature reaches its originalvalue. See Fig. 15-27.

In the following work, why is 1.4 atm multiplied by 1.013e5 pascals? And to clarify, PA=2.7 just means pressure A.
Figure 15-27
(a) Calculate the total work done by the gas in the process (in joules).
Work done by gas along the parts BC W2= PdV
= P( Vc-Vb)

= 1.4*1.013*105( 13.1-6.8)*10-3
=893.466J

It's a unit conversion. The equation requires that the pressure be in pascals, and 1 atm = 1.01325 x 105 pascals.
 
  • #3
So to get to joules of work, you have to multiply pascals times volume? And why is the answer divided by a thousand (10^-3)?
 
  • #4
gibson101 said:
So to get to joules of work, you have to multiply pascals times volume? And why is the answer divided by a thousand (10^-3)?

Because the volume should be in cubic meters, and the values given in liters. How many liters in a cubic meter?
 
  • #5
1 liter = .001 m^3. So pascals times cubic meters equals joules? I'm confused.
 
  • #6
gibson101 said:
1 liter = .001 m^3. So pascals times cubic meters equals joules? I'm confused.

No need to be confused. Pressure x volume does indeed have the units of energy.
 

FAQ: Why multiply atm by atmospheric pressure in pascals?

1. Why do we need to convert between atm and pascals?

Both atm (atmospheric pressure) and pascals (SI unit for pressure) are commonly used to measure pressure. Converting between the two units allows us to make accurate calculations and comparisons using different units of measurement.

2. What is the conversion factor between atm and pascals?

The conversion factor between atm and pascals is 1 atm = 101325 pascals. This means that 1 atm is equivalent to 101325 pascals.

3. Why is atmospheric pressure measured in atm and pascals?

Atmospheric pressure is measured in different units to cater to different needs and preferences. For example, atm is commonly used in weather reports and scuba diving, while pascals are used in scientific and engineering calculations.

4. How do I convert atm to pascals?

To convert atm to pascals, multiply the value in atm by 101325. For example, if you want to convert 2 atm to pascals, the calculation would be 2 atm x 101325 pascals/atm = 202650 pascals.

5. Why is it important to use standard units of measurement like pascals?

Using standard units of measurement like pascals ensures consistency and accuracy in scientific calculations and experiments. It also allows for easy comparison and communication of results between scientists and researchers worldwide.

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