Examples of excluded volume in the following topics:
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- The van der Waals equation modifies the Ideal Gas Law to correct for the excluded volume of gas particles and intermolecular attractions.
- As the pressure increases,
the volume of the container decreases.
- The
volume occupied by the gas particles is no longer negligible compared to the
volume of the container and the volume of the gas particles needs to be taken
into account.
- where P is the pressure, V is the volume, R is the universal gas constant, and T is the absolute temperature.
- The b term represents the excluded volume of the gas or the volume occupied by the gas particles.
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- In the term above, a is a constant specific to each gas and V is the volume. van der Waals also corrected the volume term by subtracting out the excluded volume of the gas.
- where b is the excluded volume of the gas, R is the universal gas constant, and T is the absolute temperature.
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- Real gases deviate from the ideal gas law due to the finite volume occupied by individual gas particles.
- At high pressures where the volume occupied by gas molecules does not approach zero
- The particles of a real gas do, in fact, occupy a finite, measurable volume.
- At high pressures, the deviation from ideal behavior occurs because the finite volume that the gas molecules occupy is significant compared to the total volume of the container.
- The van der Waals equation modifies the ideal gas law to correct for this excluded volume, and is written as follows:
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- (Isotherms refer to the different curves on the graph, which represent a gas' state at different pressure and volume conditions but at constant temperature; "Iso-" means same and "-therm" means temperature—hence isotherm.)
- For most applications, the ideal gas approximation is reasonably accurate; the ideal gas model tends to fail at lower temperatures and higher pressures, however, when intermolecular forces and the excluded volume of gas particles become significant.
- Real gases are often modeled by taking into account their molar weight and volume:
- b is an empirically determined factor that corrects for the excluded volume of gas particles; it is specific for each gas
- According to the Ideal Gas Equation, PV=nRT, pressure and volume should have an inverse relationship.
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- Place the standardized solution into the burette, and indicate its initial volume in a lab notebook.
- This is the first titration and it is not very precise; it should be excluded from any calculations.
- (Subtracting the initial volume from the final volume will yield the amount of titrant used to reach the endpoint.)
- The burette is calibrated to show volume to the nearest 0.001 cm3.
- Compute the concentration of an unknown acid or base given its volume and the volume and concentration of the standardized titrant.
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- A thermodynamic system can be any physical system with a well-defined volume in space.
- It includes the energy needed to create the system, but excludes the energy needed to displace the system's surrounding or energy displacement due to external forces.
- For example, if a reaction is held at constant volume, no work is performed and therefore $\Delta U=q$.
- Therefore, to account for both the possible volume change at constant pressure and the internal energy, enthalpy is used.
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- Charles' Law describes the relationship between the volume and temperature of a gas.
- This law states that at constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factor as its temperature (in Kelvin); in other words, temperature and volume are directly proportional.
- A car tire filled with air has a volume of 100 L at 10°C.
- If a gas contracts by 1/273 of its volume for each degree of cooling, it should contract to zero volume at a temperature of –273°C; this is the lowest possible temperature in the universe, known as absolute zero.
- The lower a gas' pressure, the greater its volume (Boyle's Law), so at low pressures, the fraction \frac{V}{273} will have a larger value; therefore, the gas must "contract faster" to reach zero volume when its starting volume is larger.
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- Avogadro's Law states that at the same temperature and pressure, equal volumes of different gases contain an equal number of particles.
- V is the volume of the gas, n is the number of moles of the gas, and k is a proportionality constant.
- The barrier moves when the volume of gas expands or contracts.
- What is the relationship between the number of molecules and the volume of a gas?
- (Note: Although the atoms in this model are in a flat plane, volume is calculated using 0.1 nm as the depth of the container.)
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- The effects of changes in volume and pressure on a reversible reaction in chemical equilibrium can be predicted by Le Chatelier's Principle.
- The effects of changes in volume and pressure on chemical equilibrium can be predicted using Le Chatelier's Principle.
- This principle can be applied to changes in temperature, concentration, volume, and pressure.
- One example of the effect of changing volume is shown in .
- As can be seen, a reduction in volume yields an increase in the pressure of the system, because volume and pressure are inversely related.
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- Boyle's Law describes the inverse relationship between the pressure and volume of a fixed amount of gas at a constant temperature.
- In this case, the initial pressure is 20 atm (P1), the initial volume is 1 L (V1), and the new volume is 1L + 12 L = 13 L (V2), since the two containers are connected.
- Gases can be compressed into smaller volumes.
- Run the model, then change the volume of the containers and observe the change in pressure.
- What happens to the pressure when the volume changes?