Ideal gas law problems: Pascals vs Atms?

In summary, the conversation is discussing how to properly use the ideal gas law, PV = nRT, when given values in different units. It is important to use the appropriate units and constants in order to get the correct answer. Both using SI units and other units are acceptable, as long as the correct value of R is used. If given values in different units, they can be converted to one system before solving the problem.
  • #1
ddoctor
9
0
Hi group,

Simple arithmetic problems using PV = nRT or NkT. How do you know when to use pressure units in atmospheres or pascals? For example, in 1 particular problem they give you a pressure in units of Torr, volume in cubic cm and temp in Kelvin and ask for the number of molecules. Couldn't you convert Torr to atm, cm to L OR Torr to Pascals and cm to m. In the first case you get n number of moles and multiply by avagadro's number to get molecules. In the second case you use NkT to get the number of molecules directly, probably easier, but aren't both approaches correct?
Thanks
Dave
 
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  • #2
As long as all of your units are in the same system and you use the appropriate constants (in the same units) you will be fine. Just keep track of your units to ensure that your answers make sense.
 
  • #3
My advice is:use SI-mKgs.The most correct and reliable.Sometimes involves big numbers,but,hey,where would the fun be in such problems??

Daniel.
 
  • #4
When using SI units : P is in Pa (or N/m^2), V is in m^3, T is in Kelvin and R = 8.314 J/K-mol

When using the other units : P is in atm, V is in Liters, T is in Kelvin and R = 0.0821 L-atm/K-mol

You can you any system you like. Remember to use the right value of R in that system.

If you are given values in units other than the two above (eg : torr, psi, ml, cc, centigrade, fahrenheit), you can simply convert to either one system of units.
 

Related to Ideal gas law problems: Pascals vs Atms?

1. What is the ideal gas law and how does it relate to Pascals and Atms?

The ideal gas law is a mathematical equation that describes the behavior of ideal gases. It states that the pressure (P), volume (V), and temperature (T) of an ideal gas are related by the equation PV = nRT, where n is the number of moles of gas and R is the ideal gas constant. Both Pascals and Atms are units of pressure that can be used in this equation.

2. How do I convert between Pascals and Atms in ideal gas law problems?

To convert between Pascals and Atms, you can use the conversion factor 1 atm = 101,325 Pa. This means that 1 atm is equivalent to 101,325 Pascals. So if you are given a pressure in Pascals, you can divide by 101,325 to convert to Atms, and vice versa.

3. Why do we use different units of pressure in ideal gas law problems?

Different units of pressure are used in ideal gas law problems to make calculations more convenient. For example, if you are working with very small volumes of gas, using Pascals (which are smaller units) may be more appropriate. On the other hand, if you are working with larger volumes of gas, using Atms (which are larger units) may make the numbers easier to work with.

4. How do I know when to use Pascals or Atms in ideal gas law problems?

The choice between using Pascals or Atms in ideal gas law problems depends on the specific situation and what units are given in the problem. If the pressure is given in Pascals, it may be more convenient to use Pascals in the calculations. If the pressure is given in Atms, it may be more appropriate to use Atms in the calculations. It is important to pay attention to units and make sure they are consistent throughout the problem.

5. Can I use other units of pressure in ideal gas law problems?

Yes, you can use other units of pressure in ideal gas law problems as long as you convert them to either Pascals or Atms. Some other common units of pressure include torr, mmHg, and psi. You can use conversion factors to convert these units to either Pascals or Atms before plugging them into the ideal gas law equation.

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