Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: fogy on December 31, 2011, 09:41:12 AM
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The rotational constant B for H35Cl was measured to be 10.5909 cm-1. Calculate the values for H37Cl and 2D35Cl.
B=h/(8pi^2)(I)(c)
10.5909= h/(8pi^2)(I)(c)
do I find the moment of inetira (I) this way for H35CL? ...and then calculate the reduced mass for H37CL? Then giving me a new value for I by the equation ..r squared = u/I
Where or how would i get the value for the bond length/ internecleur distance (these are the same right?) so i could calculate the new I
Maybe im doing this whole question wrong.
Help would be appriciated
Thanks :)
Thanks :)
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Assume bond length doesn't change. You don't need to know its exact value.
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Assume bond length doesn't change. You don't need to know its exact value.
H35Cl: B= 10.5909cm^-1
reduced mass for H37CL is calculated to be : 2.8003*10^-54Kg
Now im thinking that if i want to calculate B for this specific compound il need to use B= h/8pi^2 (I)(c) Missing I here so need to calculate that by using : I=(R^2)(U)
But then see that i need R ( bond length figure) to be able to calculate I and so B.
There is obviously another way of doing this so that you dont need the bond length figure?
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Starting with
$$ B = \frac h {8\pi^2cI} $$
and remembering that
$$ I = \mu R^2 $$
you can easily get
$$ \frac {B_{H^{35}Cl}} {B_{H^{37}Cl}} = \frac {\mu_{H^{37}Cl}} {\mu_{H^{35}Cl}} $$
(edit: that is, assuming R is constant).
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I understand now, thanks a mil!! :D