What Does the Area Under the Molecular Speed Distribution Curve Represent?

AI Thread Summary
The area under the molecular speed distribution curve represents the total number of molecules with speeds within a specific range. This is related to the Boltzmann distribution, where the y-axis indicates the number of molecules at various speeds. The total area under the curve corresponds to the total number of molecules in the system. Additionally, the area between two specific speeds indicates the number of molecules that possess speeds within that range. Understanding this concept is essential for analyzing molecular behavior in gases.
nithin
Messages
29
Reaction score
0
hi guys i gota question in chemistrygas laws , i thought about it and am still confused ~~~~~~~~~~~ what does the area under a number of molecules against speed of gas represent? it is to do with root mean square speed ... i thought that it might be the average kinetic energey but it seems unlikely to be so ... just for reference "[PLAIN Gases/Kinetic/Gases08.htm"][URL]http://wine1.sb.fsu.edu/.../[/URL] Gases/Kinetic/Gases08.htm[/URL]
 
Last edited by a moderator:
Physics news on Phys.org
lol...it means the no. of molecules present...bad boy...neva read textbook!
 
number of molecules? why?
 
nithin said:
hi guys i gota question in chemistrygas laws , i thought about it and am still confused ~~~~~~~~~~~ what does the area under a number of molecules against speed of gas represent? it is to do with root mean square speed ... i thought that it might be the average kinetic energey but it seems unlikely to be so ... just for reference "[PLAIN Gases/Kinetic/Gases08.htm"][URL]http://wine1.sb.fsu.edu/.../[/URL] Gases/Kinetic/Gases08.htm[/URL][/QUOTE]1. That URL is incomplete - please fix it.

2. Are you referring to the Boltzmann distribution of molecular speeds? The y-axis represents the number of molecules whose speeds lie within some v and v+dv.

3. For any collection of particles (eg:molecules), you can define what is known as a molecular distribution function, f(r,v,t) which is the mean number of molecules whose center of mass at time t is found between r and r+dr and whose velocities lie between v and v+dv. The y-axis of the Boltzmann curve is like the time averaged distribution independent of position, [itex]n(v) = (1/T) \int_0^T dt \int_{box} d^3r f(r,v,t) [/itex]

4. The mean square velocity is simply [itex] (1/T) \int dt \int d^3r \int d^3v f(r,v,t) v^2 [/itex]. The RMS velocity is the square root of this number.

5. The total area under the Boltzmann curve [itex] (1/T) \int dt \int d^3r \int d^2v f(r,v,t) [/itex] is the number of molecules that can be found at any position, possessing any velocity, ie: the total number of molecules in the box.

6. The area under the curve between two speeds v1 and v2 represents the total number of molecules having speeds between v1 and v2.
 
Last edited by a moderator:
Thread 'Confusion regarding a chemical kinetics problem'
TL;DR Summary: cannot find out error in solution proposed. [![question with rate laws][1]][1] Now the rate law for the reaction (i.e reaction rate) can be written as: $$ R= k[N_2O_5] $$ my main question is, WHAT is this reaction equal to? what I mean here is, whether $$k[N_2O_5]= -d[N_2O_5]/dt$$ or is it $$k[N_2O_5]= -1/2 \frac{d}{dt} [N_2O_5] $$ ? The latter seems to be more apt, as the reaction rate must be -1/2 (disappearance rate of N2O5), which adheres to the stoichiometry of the...
Back
Top