# Since PV=nRT is used the gas

• initiator
In summary, PV=nRT is the ideal gas law equation used to calculate the properties of an ideal gas under different conditions. The pressure, volume, temperature, and number of moles are measured in units of atm, L, K, and mol respectively, with the gas constant having varying units. While it is not accurate for real gases, it can be used as an approximation. According to PV=nRT, changes in one variable affect the others in an inverse or direct relationship. This equation has practical applications in various scientific fields and can be used to solve problems related to gas behavior.

#### initiator

suppose an Q amount of heat is given to a system initially at v_1 & p_1 vol and pressure. and the system does a equal amt of work on the surroundings so that delU=0. but in doing this work system has expanded to volume v_2 and has a pressure p_2 due to which it is at a different position on the P-V curve. is it possible that two points on the PV curve represent the same state.

Is free expansion of a gas a reversible process if so how p_ext in this case is always far lower than p_int and the system is never in equilibrium through out the process. how can be then free expansion achieved reversibly. (for the process to be reversible p_ext shuld be infinitesimal greater than p_int isn't it so?)

In case of enthalpy delH=delU + deln_g(RT). this relation is derived assuming that the process is isothermal. and since PV=nRT is used the gas is assumed to be ideal then why in this case is delU is not taken as zero? where n_g is the difference between the no of moles of product formed and the moles on the reactant side.

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initiator said:
suppose an Q amount of heat is given to a system initially at v_1 & p_1 vol and pressure. and the system does a equal amt of work on the surroundings so that delU=0. but in doing this work system has expanded to volume v_2 and has a pressure p_2 due to which it is at a different position on the P-V curve. is it possible that two points on the PV curve represent the same state.

Of course, for isothermal expansion of an ideal gas, the final state can be the same as the initial state if no expansion has occurred.

Is free expansion of a gas a reversible process if so how p_ext in this case is always far lower than p_int and the system is never in equilibrium through out the process. how can be then free expansion achieved reversibly. (for the process to be reversible p_ext shuld be infinitesimal greater than p_int isn't it so?)
Free expansion is always irreversible. For expansion to be reversible, the expansion must be quasi static such that the external pressure is only slightly less than the mean pressure of the gas.
In case of enthalpy delH=delU + deln_g(RT). this relation is derived assuming that the process is isothermal. and since PV=nRT is used the gas is assumed to be ideal then why in this case is delU is not taken as zero? where n_g is the difference between the no of moles of product formed and the moles on the reactant side.
The internal energy of an ideal gas reaction mixture is not a function only of temperature. It changes as a result of making and breaking chemical bonds, so that there are changes in the amounts of the various chemical species that are present. So, when a chemical reaction occurs at constant temperature, ##\Delta U## is not equal to zero.

## What is PV=nRT and how is it used?

PV=nRT is the equation for the ideal gas law, which relates the pressure, volume, temperature, and number of moles of a gas. It is used to calculate the properties of an ideal gas under various conditions.

## What are the units for each variable in PV=nRT?

The pressure (P) is typically measured in atmospheres (atm), volume (V) in liters (L), temperature (T) in Kelvin (K), and number of moles (n) in moles (mol). The gas constant (R) has different units depending on the units used for the other variables.

## Can PV=nRT be used for real gases?

PV=nRT is an idealized equation that assumes the gas particles have no volume and do not interact with one another. Therefore, it is not accurate for real gases, but it can still be used as an approximation under certain conditions.

## How does changing one variable affect the others in PV=nRT?

According to PV=nRT, pressure and volume are inversely proportional, while temperature and volume are directly proportional. This means that as one variable increases, the other decreases, and vice versa. The number of moles and the gas constant are typically constant in most situations.

## What are some practical applications of PV=nRT?

PV=nRT is used in many scientific fields, including chemistry, physics, and engineering. It is used to predict the behavior of gases in various systems and can be applied to problems such as calculating the volume of a gas at a given pressure and temperature or determining the amount of gas produced in a chemical reaction.