Joules or KJ?

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Veronica Lu 2H
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Joules or KJ?

Postby Veronica Lu 2H » Mon Feb 10, 2020 10:06 pm

when solving problems on the midterm, are we supposed to have final answers in J or kJ? or does it depend on the problem?

Paul Hage 2G
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Joined: Thu Jul 25, 2019 12:17 am

Re: Joules or KJ?

Postby Paul Hage 2G » Mon Feb 10, 2020 10:08 pm

Unless the problem specifies whether we should have our answer in Joules or kilojoules, I believe we could write our answer using either unit. The important thing is to make sure the units for different variables in a specific problem match.

Daniel Yu 1E
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Joined: Sat Aug 24, 2019 12:15 am

Re: Joules or KJ?

Postby Daniel Yu 1E » Mon Feb 10, 2020 10:09 pm

I'm pretty sure it really doesn't matter whether you leave it Joules or KJ, as long as you convert correctly. I'm assuming if the quantities are given to you in KJ you would leave it as KJ, and the same for Joules, but it doesn't really matter as long as you have the same answer.

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

Re: Joules or KJ?

Postby 305421980 » Mon Feb 10, 2020 10:13 pm

I think it depends on what the problem asks for but generally doesn't matter. I would just be careful and make sure when solving everything is matching. Also I know that a lot of times enthalpies use KJ whereas entropy is often in J. So I would just be conscience of units as you go.

BNgo_2L
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Re: Joules or KJ?

Postby BNgo_2L » Mon Feb 10, 2020 10:19 pm

It usually doesn't matter unless specified. However, the correct number of significant figures will determine if you write your answer in kJ or J.

Uisa_Manumaleuna_3E
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Joined: Wed Sep 21, 2016 2:56 pm

Re: Joules or KJ?

Postby Uisa_Manumaleuna_3E » Wed Feb 12, 2020 9:11 pm

Also, it also kinda helps to look at the answer you have and see which one (J/KJ) just makes more sense. Like, for some answers I would get something long like 1000000 J and that would be appropriate for the question. But like it just made more sense to shorten it to 1000 kj.

But yeah, they're both basically the same. Just do the normal rule of thumb and make sure all the units cancel out. Those are important.

Tiffany_Chen 2K
Posts: 106
Joined: Fri Aug 30, 2019 12:15 am

Re: Joules or KJ?

Postby Tiffany_Chen 2K » Wed Feb 12, 2020 9:37 pm

Just make sure the constants you use (e.g. R), will match the units you want. Really depends on what the question asks for.

Robin Cadd 1D
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Joined: Thu Jul 11, 2019 12:16 am

Re: Joules or KJ?

Postby Robin Cadd 1D » Thu Feb 13, 2020 2:38 pm

I don't think it matters.

Gurmukhi Bevli 4G
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Joined: Wed Nov 14, 2018 12:20 am

Re: Joules or KJ?

Postby Gurmukhi Bevli 4G » Sat Feb 15, 2020 3:59 am

I don't think it matters provided your units stay consistent throughout the entire problem. If J/kJ are necessary the problem will probably specify which unit it wants/if it wants you to convert between units.

Veronica_Lubera_2A
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Re: Joules or KJ?

Postby Veronica_Lubera_2A » Sat Feb 15, 2020 12:00 pm

You should always check the units in the constants you plug into your formulas. So it would depend whether it's joules or kilojoules.

Callum Guo 1H
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Re: Joules or KJ?

Postby Callum Guo 1H » Sat Feb 15, 2020 3:19 pm

I don't think it matters unless the question specifically asks for a unit

Nuoya Jiang
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Re: Joules or KJ?

Postby Nuoya Jiang » Sat Feb 15, 2020 3:49 pm

Most of the time J.

Anish Natarajan 4G
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Joined: Thu Jul 25, 2019 12:16 am

Re: Joules or KJ?

Postby Anish Natarajan 4G » Sun Feb 16, 2020 1:11 pm

Both work but I'd be careful to convert all your units to the same scale (either joules or kilojoules) because the equations we use for entropy give us the answer in joules whereas the equations we use to calculate enthalpy frequently use kilojoules

pmokh14B
Posts: 107
Joined: Sat Aug 17, 2019 12:15 am

Re: Joules or KJ?

Postby pmokh14B » Sun Feb 16, 2020 1:11 pm

Either works, unless it's specified in the problem.

Natalie Benitez 1E
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Joined: Fri Aug 02, 2019 12:15 am

Re: Joules or KJ?

Postby Natalie Benitez 1E » Sun Feb 16, 2020 2:27 pm

Why does entropy and enthalpy have different units?


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