What is the effect of decomposing one mole of gas on temperature?

In summary, the pressure increases, the temperature stays the same, and the pressure and temperature are in equilibrium.
  • #1
Ahmed Abdullah
203
3
One mole of certain gas is confined in a container. Suppose every molecule has decomposed and given rise to- two new molecules. Let's assume (for this purpose ) it requires negligible amount of energy for the molecule to decompose (or not any energy at all). So what will we observe?
The amount of matter has been doubled by the process, so pressure should increase- that's obvious. What happens to the temperature?
Does it stay the same OR increase?
 
Chemistry news on Phys.org
  • #2
I think I have got it. If the two newly formed molecules have the same mass then the pressure should not increase rather the temperature is halved. It is because temperature is something proportional to kinetic energy. . When a molecule is splitted to two new similliar molecule then the energy is divided between them each having halve of the original (energy is conserved). So temperature falls nothing happens to pressure.
Am I right? Please help.
 
  • #3
Ahmed Abdullah said:
I think I have got it. If the two newly formed molecules have the same mass then the pressure should not increase rather the temperature is halved. It is because temperature is something proportional to kinetic energy. . When a molecule is splitted to two new similliar molecule then the energy is divided between them each having halve of the original (energy is conserved). So temperature falls nothing happens to pressure.
Am I right? Please help.
I would say yes.
 
  • #4
It depends on the process and what the constraints are. You have an endothermic reaction that increases the number of moles of gas. You can:

- Decompose by heating slowly, which increases pressure at constant temperature
- Decompose by increasing volume slowly, which decreases temperature at constant pressure
- Combine activities or conduct the process irreversibly, which could result in a combination of changing temperature and pressure.
 
  • #5
Ahmed Abdullah said:
One mole of certain gas is confined in a container. Suppose every molecule has decomposed and given rise to- two new molecules. Let's assume (for this purpose ) it requires negligible amount of energy for the molecule to decompose (or not any energy at all). So what will we observe?
The amount of matter has been doubled by the process, so pressure should increase- that's obvious. What happens to the temperature?
Does it stay the same OR increase?

The total number of moles changes and you have an entropy change if you can recall there's an equation S=Q/T

Also note that such a reaction is going to have an enthalpy component due to the changes in bonds.
 

1. Does temperature decrease with altitude?

Yes, temperature typically decreases with altitude. This is due to the decrease in air pressure as altitude increases, which causes the air molecules to spread out and become less dense. As a result, the air cannot hold as much heat, leading to a decrease in temperature.

2. Is there a certain point at which temperature stops decreasing with altitude?

Yes, there is a point called the tropopause where the temperature stops decreasing with altitude. This is the boundary between the troposphere and the stratosphere, and it varies in height depending on factors such as latitude and season.

3. Does temperature always decrease at the same rate with altitude?

No, the rate at which temperature decreases with altitude can vary depending on atmospheric conditions. In general, the temperature decrease is more rapid in the lower levels of the atmosphere and slows down at higher altitudes.

4. Can temperature also decrease horizontally?

Yes, temperature can also decrease horizontally. This is often seen in weather systems, where cold air meets warm air and creates a temperature gradient. The temperature can also decrease horizontally due to factors such as wind and ocean currents.

5. Can temperature decrease without any external factors?

No, temperature cannot decrease without any external factors. The laws of thermodynamics state that energy cannot be created or destroyed, only transferred. Therefore, a decrease in temperature must be caused by a transfer of energy, such as heat loss to the surrounding environment.

Similar threads

What does "limit of zero pressure" mean for ideal gas temperature?
    • Chemistry
Replies
14
Views
2K
I Compressing gas with piston: reasons for temperature increase?
    • Thermodynamics
Replies
5
Views
2K
I Variation of air temperature with altitude
    • Classical Physics
Replies
27
Views
897
Dalton's law for ideal gases at different temperatures
    • Chemistry
Replies
17
Views
2K
I Modeling the concentration of gas constituents in a Force Field
    • Thermodynamics
Replies
6
Views
691
Complete thermal decomposition of specific compounds
    • Chemistry
Replies
4
Views
1K
Gas temperature in a constant volume
    • Introductory Physics Homework Help
Replies
8
Views
910
I Yet again about (real) gas compression
    • Thermodynamics
Replies
20
Views
2K
Dalton's atomic theory, Avogadro, and caloric theory
    • Chemistry
Replies
4
Views
2K
B What causes the drop of latent heat at lower temperatures in liquid helium?
    • Atomic and Condensed Matter
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top