### Kg vs Grams

Posted:

**Sat Oct 27, 2018 5:01 pm**Is there a reason we use kg in DeBroglie's equation? And in what other equations do we use kg as opposed to grams?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=18&t=34955

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Posted: **Sat Oct 27, 2018 5:01 pm**

Is there a reason we use kg in DeBroglie's equation? And in what other equations do we use kg as opposed to grams?

Posted: **Sat Oct 27, 2018 5:09 pm**

We deal with Kg in DeBroglie's equation because in that equation we are dealing with momentum. Momentum is measured in kg*ms/s. We use kg in equations that deal with momentum, energy (Joules), etc. because those values are measured with kg in it. For example the units of joules is kg⋅m^2/s^2.

Posted: **Sat Oct 27, 2018 5:44 pm**

Within this class, I believe that we will only be using kg when dealing with energy and momentum.

Posted: **Sat Oct 27, 2018 7:23 pm**

It's kinda confusing that we use kg because all the other units we use don't use kilo. E.g. the SI unit for distance is meter, not kilometer; we use mols, not kilomols.

However, for mass, the SI unit is kilograms as other units use kg. E.g joules, which is measured in kg⋅m2⋅s−2.

However, for mass, the SI unit is kilograms as other units use kg. E.g joules, which is measured in kg⋅m2⋅s−2.

Posted: **Sun Oct 28, 2018 11:04 am**

I think something that would help would be to write out the units for all parts of the equation. In h/mv, h is given in kg.m^2.s^-1. In order to cancel out the kg, the mass "m" needs to be in kilograms as well. The velocity should cancel out m.s^-1 and leave meters for λ.

Posted: **Sun Nov 04, 2018 9:38 pm**

Kg is an SI unit so always convert to Kg

Posted: **Sun Nov 04, 2018 9:49 pm**

Kg is the SI unit. We only use grams when working with moles. Always convert to kg.