## Calculate using kg or g?

AGaeta_2C
Posts: 112
Joined: Wed Sep 18, 2019 12:21 am

### Calculate using kg or g?

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?

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
Posts: 153
Joined: Fri Aug 30, 2019 12:16 am

### Re: Calculate using kg or g?

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
Posts: 111
Joined: Fri Aug 09, 2019 12:16 am

### Re: Calculate using kg or g?

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
Posts: 99
Joined: Sat Sep 07, 2019 12:19 am

### Re: Calculate using kg or g?

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
Posts: 35
Joined: Thu Jul 11, 2019 12:17 am

### Re: Calculate using kg or g?

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?

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

sbottomley3a
Posts: 50
Joined: Wed Sep 18, 2019 12:19 am

### Re: Calculate using kg or g?

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
Posts: 56
Joined: Sat Aug 17, 2019 12:18 am

### Re: Calculate using kg or g?

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?

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
Posts: 45
Joined: Fri Aug 09, 2019 12:16 am

### Re: Calculate using kg or g?

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

CalvinTNguyen2D
Posts: 102
Joined: Thu Jul 25, 2019 12:16 am

### Re: Calculate using kg or g?

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
Posts: 107
Joined: Sat Aug 17, 2019 12:17 am

### Re: Calculate using kg or g?

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?

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.