### pV=nRT

Posted:

**Thu Jan 31, 2019 8:12 pm**What is pV=nRT used for?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=123&t=41100

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Posted: **Thu Jan 31, 2019 8:12 pm**

What is pV=nRT used for?

Posted: **Thu Jan 31, 2019 8:31 pm**

pV = nRT is the ideal gas law. This is incredibly useful in calculating an unknown (for example, if you are given pressure, volume, and temperature, you can use this law to find the number of moles).

In practice problems, this is often the first step before doing other calculations (such as solving for work).

In practice problems, this is often the first step before doing other calculations (such as solving for work).

Posted: **Fri Feb 01, 2019 2:33 pm**

The ideal gas law demonstrates the relationships between pressure, volume, moles, and temperature. It is crucial to finding different values.

Posted: **Fri Feb 01, 2019 5:09 pm**

This equation shows the relationship between pressure, volume, moles, gas constant, and temperature and can be moved around to find these different values.

Posted: **Fri Feb 01, 2019 6:41 pm**

This equation if the Ideal Gas Law and relationships between the different variables could be derived from this equation:

Boyle's Law: at constant T and n, V and p have an inverse relationship (pV = constant), p1V1 = p2V2

Charles' Law: at constant p and n, V and T have a direct relationship (V/T = constant), V1T1 = V2T2

Avogadro's Law: at constant T and p, V and n have a direct relationship (V/n = constant), V1n1=V2n2

It can be used to determine the molar mass of gases and volatile liquids as n=m(mass)/M(molar mass),

pV=nRT=RT(m/M) -> M=mRT/pV --(1)

It can also be used to determine the density of a gas:

m/V=pM/RT (derived from (1)) -> m/V=pM/RT -> density = pM/RT

Boyle's Law: at constant T and n, V and p have an inverse relationship (pV = constant), p1V1 = p2V2

Charles' Law: at constant p and n, V and T have a direct relationship (V/T = constant), V1T1 = V2T2

Avogadro's Law: at constant T and p, V and n have a direct relationship (V/n = constant), V1n1=V2n2

It can be used to determine the molar mass of gases and volatile liquids as n=m(mass)/M(molar mass),

pV=nRT=RT(m/M) -> M=mRT/pV --(1)

It can also be used to determine the density of a gas:

m/V=pM/RT (derived from (1)) -> m/V=pM/RT -> density = pM/RT

Posted: **Fri Feb 01, 2019 8:11 pm**

What does the R in this equation stand for?

Posted: **Fri Feb 01, 2019 8:13 pm**

is is a given constant! should be in the equations sheet or in the problem

Posted: **Fri Feb 01, 2019 9:20 pm**

In addition to the many uses labeled above, you can also use the law to calculate work in a constant-pressure system (-P*deltaV) when you are not given either the change in volume or the pressure because assuming that you have been given the change in the moles of gas in the reaction, you can equate P*(delta V) to (delta n)*R*T, with RT being a constant. Dr. Lavelle did an example problem like this in lecture today.

Posted: **Sat Mar 02, 2019 7:03 pm**

You can use pv=nrt to find one of the constants like n,t,p,or v.

Posted: **Sat Mar 02, 2019 7:06 pm**

PV=NRT is a very versatile equation. You can use it for questions that want you to find a missing variable in the equation after plugging everything in.

Posted: **Sat Mar 02, 2019 10:52 pm**

We can use it to solve for variables that might be unknown to us from the problem.

Posted: **Sun Mar 03, 2019 10:01 pm**

You can use the equation to find any of the variables, so p,V,n and T. R is a constant.

Posted: **Sat Mar 16, 2019 12:55 pm**

it can also be used to replace pV with nRT in some equations