Calculate using kg or g?

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AGaeta_2C
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Calculate using kg or g?

Postby AGaeta_2C » Sun Oct 06, 2019 10:31 pm

In lecture 3, one of the powerpoint slides said:
SI Fundamental (Base) Units: mass (kg) length (m) time (s)
Why is the kilo- prefix added for the unit for mass?
Are we supposed to convert all the masses to kg before our calculations?

However later I think either the professor or the lecture slide said something about "before calculations, convert all prefixes to the volume of 10 they represent." This part leads me to believe that we have to preform all our calculations using grams in the equation.

Can anybody clear this up for me? Thank you :)

Chem_Mod
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Re: Calculate using kg or g?

Postby Chem_Mod » Sun Oct 06, 2019 10:34 pm

The kg is the SI unit of mass and you will have to convert most masses to kg for calculations. However, this will depend on the question asked and what you are solving for.

Sarah Blake-2I
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Re: Calculate using kg or g?

Postby Sarah Blake-2I » Sun Oct 06, 2019 10:48 pm

For when it asks for mass at least for this test and the homework problems, I think we leave the answer in grams :)

claudia_1h
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Joined: Fri Aug 09, 2019 12:16 am

Re: Calculate using kg or g?

Postby claudia_1h » Sun Oct 06, 2019 10:58 pm

The solutions manual for the textbook gives most answers in grams, so I'm assuming the answers are okay to be left in grams, unless the question specifically asks for the answer in kg.

Indy Bui 1l
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Joined: Sat Sep 07, 2019 12:19 am

Re: Calculate using kg or g?

Postby Indy Bui 1l » Sun Oct 06, 2019 11:05 pm

It depends on the question. If you are using a formula that requires kg then of course convert to kg for the calculations or vice versa. In terms of your answer, I don't believe you will be marked incorrect for either form. Use proper judgement, if the question asks for your answer in grams then do that.

305376058
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Joined: Thu Jul 11, 2019 12:17 am

Re: Calculate using kg or g?

Postby 305376058 » Sun Oct 13, 2019 9:29 pm

I think that leaving the answer in grams is okay, but it might depend on the question being asked.

Kassidy Ford 1I
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Re: Calculate using kg or g?

Postby Kassidy Ford 1I » Fri Oct 18, 2019 8:57 am

I think different equations are in terms of kg, while some you can use grams. For molar mass, obviously use grams

sbottomley3a
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Joined: Wed Sep 18, 2019 12:19 am

Re: Calculate using kg or g?

Postby sbottomley3a » Fri Oct 18, 2019 10:11 am

I think that a good rule of thumb is to give the answer in grams, unless the question specifies kilograms. We usually need to convert to grams to use the molar mass conversions, so at least we're already there!

405404782 Gabriel Rigole 4F
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Re: Calculate using kg or g?

Postby 405404782 Gabriel Rigole 4F » Sun Oct 20, 2019 3:56 pm

I believe that the unit asked in the question will also be used in your final answer.

Robert Cross 1A
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Joined: Wed Sep 11, 2019 12:15 am

Re: Calculate using kg or g?

Postby Robert Cross 1A » Sun Oct 20, 2019 8:01 pm

In my experience with high school chem + this course, it seems like chemistry calculations tend to be mostly done with grams. If they specifically ask you to provide an answer with another unit of mass, use that unit, but generally grams are the unit of measure used.

emwoodc
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Joined: Fri Aug 09, 2019 12:16 am

Re: Calculate using kg or g?

Postby emwoodc » Mon Oct 21, 2019 4:35 pm

you can't go wrong with always answer using grams and converting early on wouldn't hurt.

CalvinTNguyen2D
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Re: Calculate using kg or g?

Postby CalvinTNguyen2D » Sun Oct 27, 2019 11:49 pm

It'll depend mostly on the equation that you need to use, but generally we use grams for molar conversions and kilograms for calculations involving spectrography.

Timmy Nguyen Dis 1I
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Joined: Sat Aug 17, 2019 12:17 am

Re: Calculate using kg or g?

Postby Timmy Nguyen Dis 1I » Sun Nov 03, 2019 2:46 pm

I think both are fine. Just do what the question is asking, and pay attention to the different units when doing dimensional analysis. For example, remember to convert to kg if you're going to use a formula involving Joules, because Joules is kg * m^2 * s^-2

305421980
Posts: 101
Joined: Sat Sep 07, 2019 12:16 am

Re: Calculate using kg or g?

Postby 305421980 » Sun Nov 03, 2019 5:30 pm

For most questions involving energy and J, you should convert to kg because the SI base unit is integral in the units. However, a lot of times it is okay just to use grams. It really depends on the units asked for on the specific question.


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