Calculating Proton-Proton Distance in CaSO4.2H2O with CGS-Units

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In summary, the conversation discusses the difficulties with using CGS-units in an experiment involving NMR and calculating the proton-proton distance in CaSO4.2H2O. The formula used requires converting u0 to 1 and there may be other changes in the formula when using CGS-units. The speaker suggests doing calculations in SI units first and then converting to CGS units to avoid confusion.
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Henk
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I'm having great difficulties with CGS-units. In an experiment involving NMR I have to calculate the proton-proton distance in CaSO4.2H2O.

I have done the measurements and they are, I think, pretty good however I have some problems with the calculations because of the units.

The formula I have to use is the following:

a = (3/2)(u*u0)/r^3

where u = 2.79*5.05*10^-27 J/T = 2.79*5.05*10^-24 erg/Gauss and u0 is the Permeability of vacuum. a is something I measured and has a value of 4.5 Gauss.

I know that r should be about 1.5 Angstrom (spelling?). My instructor told me to use CGS-units (thus putting u0=1) but does that mean that the rest of the formula stays the same? Or are there other changes like an additional 4pi or something. If I just put u0=1 I get r = 1.67*10^-8 (but I don't know the units, I believe the CGS-unit for distance is cm in which case r=1.67*10^-10 m = 1.67 A which is pretty close to 1.5 A).
 
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  • #2
Henk said:
I'm having great difficulties with CGS-units. In an experiment involving NMR I have to calculate the proton-proton distance in CaSO4.2H2O.
I have done the measurements and they are, I think, pretty good however I have some problems with the calculations because of the units.
The formula I have to use is the following:
a = (3/2)(u*u0)/r^3
where u = 2.79*5.05*10^-27 J/T = 2.79*5.05*10^-24 erg/Gauss and u0 is the Permeability of vacuum. a is something I measured and has a value of 4.5 Gauss.
I know that r should be about 1.5 Angstrom (spelling?). My instructor told me to use CGS-units (thus putting u0=1) but does that mean that the rest of the formula stays the same? Or are there other changes like an additional 4pi or something. If I just put u0=1 I get r = 1.67*10^-8 (but I don't know the units, I believe the CGS-unit for distance is cm in which case r=1.67*10^-10 m = 1.67 A which is pretty close to 1.5 A).

Why don't you do the calculations first in SI units, and convert in the end in CGS ? I also get confused often between CGS, Gaussian, Natural,... etc units concerning EM quantitities because indeed, some include a 4 pi, others don't etc...

So I then do everything in SI units, and fill in the 4 pi in the other units in order to obtain the same result :blushing:
 

Related to Calculating Proton-Proton Distance in CaSO4.2H2O with CGS-Units

1. How do you calculate the proton-proton distance in CaSO4.2H2O using CGS units?

To calculate the proton-proton distance in CaSO4.2H2O using CGS units, you will need to use the formula r = q1q2/4πεr, where q1 and q2 are the charges of the protons, and ε is the permittivity of free space. The value of ε in CGS units is 1/4π, so the equation simplifies to r = q1q2. Once you have calculated the distance, you can convert it to the desired unit using appropriate conversion factors.

2. What is the significance of calculating the proton-proton distance in CaSO4.2H2O?

Calculating the proton-proton distance in CaSO4.2H2O is significant because it can help us understand the forces between protons in this compound. This information is important in fields such as chemistry, material science, and biology, where understanding the interactions between atoms and molecules is crucial.

3. Can the proton-proton distance in CaSO4.2H2O be measured experimentally?

Yes, the proton-proton distance in CaSO4.2H2O can be measured experimentally using techniques such as X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. These methods allow scientists to determine the positions of atoms in a molecule and calculate the distances between them.

4. How does the proton-proton distance in CaSO4.2H2O affect the properties of the compound?

The proton-proton distance in CaSO4.2H2O can affect the properties of the compound in several ways. For example, a shorter distance between protons indicates a stronger electrostatic force, which can impact the solubility, melting point, and other physical properties of the compound. Additionally, the proton-proton distance can also affect the chemical reactivity and stability of the compound.

5. Are there any limitations to calculating the proton-proton distance in CaSO4.2H2O with CGS units?

One limitation of using CGS units to calculate the proton-proton distance in CaSO4.2H2O is that it does not take into account the quantum nature of particles, such as protons. Additionally, the calculation assumes that the charges are point particles, which may not be accurate for some molecules. It is also important to note that the accuracy of the calculation depends on the accuracy of the experimental data used for the charges and the permittivity of free space.

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