## SI Base Unit Kg

Brendan Duong 1I
Posts: 69
Joined: Wed Sep 30, 2020 10:07 pm

### SI Base Unit Kg

If Kg is the base unit we use in chemistry (as opposed to grams which seems weird to me), then does that mean all future formulas we use involving mass should be with kg? For example Ek=0.5me-*ve-^2 where me- is in kg?

Andrew Jubintoro 3J
Posts: 118
Joined: Wed Sep 30, 2020 9:58 pm
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### Re: SI Base Unit Kg

I think that it really depends on what other units are involved in the formula.
For example kinetic energy has the unit Joules or $kg\cdot m^2\cdot s^{-2}$ so it makes sense to use kilograms when calculating for kinetic energy.
On the other hand if you are given the mass of a substance in grams and were asked to calculate its amount in moles, then there is no need to convert the mass to kilograms because the molar mass you would use will be in $g\cdot mol^{-1}$

Becca Nelson 3F
Posts: 103
Joined: Wed Sep 30, 2020 9:52 pm

### Re: SI Base Unit Kg

As a general rule of them look at the unit in the equations you are using. While kilograms is the SI unit, there are many lab instances where using grams is preferred. Just make sure to always check the equation and what it requires (g or kg) and to see what units the final answer asks for and do you math accordingly.

Zainab Jamali 1H
Posts: 100
Joined: Wed Sep 30, 2020 9:54 pm

### Re: SI Base Unit Kg

Becca Nelson 1J wrote:As a general rule of them look at the unit in the equations you are using. While kilograms is the SI unit, there are many lab instances where using grams is preferred. Just make sure to always check the equation and what it requires (g or kg) and to see what units the final answer asks for and do you math accordingly.

This is a good point! Often times, even though m^3 is the SI unit for volume a lot of chemistry problems will give values or ask for answers in mL or L.
Last edited by Zainab Jamali 1H on Thu Oct 08, 2020 11:02 pm, edited 1 time in total.

OwenSumter_2F
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### Re: SI Base Unit Kg

Also, using g or mg or any other unit like that is perfectly fine, it is just a convenience for us. It would be very annoying having to write 3.2x10-6kg in every lab working with small amounts.

Grace_Remphrey_2J
Posts: 90
Joined: Wed Sep 30, 2020 9:54 pm

### Re: SI Base Unit Kg

I would recommend using the units that the initial problem uses unless the problem states for you to change the units in your final answer. Hope this helps!