Negative and Positive values of delta H and w

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405112316
Posts: 62
Joined: Fri Sep 28, 2018 12:17 am

Negative and Positive values of delta H and w

Postby 405112316 » Tue Feb 12, 2019 5:22 pm

Can someone explain the transfer of energy that happens when both delta H and w are negative and positive?

I know the when work is positive, energy is going into the system. This means that some sort of pressure is condensing the system or the volume is getting smaller.

When delta H is negative, is heat flowing into the system or leaving the system?

Jim Brown 14B Lec1
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

Re: Negative and Positive values of delta H and w

Postby Jim Brown 14B Lec1 » Tue Feb 12, 2019 5:23 pm

A negative Delt. H means a -q (heat loss)

Anna O 2C
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Joined: Fri Sep 28, 2018 12:19 am

Re: Negative and Positive values of delta H and w

Postby Anna O 2C » Sun Feb 17, 2019 6:40 pm

A negative delta H means that the heat transfer is negative and thus the system is losing heat.

KarlaArevalo2F
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Re: Negative and Positive values of delta H and w

Postby KarlaArevalo2F » Sun Feb 17, 2019 9:42 pm

-delta H means the system is exothermic and is releasing heat (surrounding absorb that heat) and + delta H means the system is endothermic and requires heat

Melissa Bu 1B
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Re: Negative and Positive values of delta H and w

Postby Melissa Bu 1B » Mon Feb 18, 2019 10:19 am

w>0 means work is being done on the system
w<0 means work is being done by the system
H>0 means the system requires heat (heat flows in)
H<0 means the system release heat (heat flows out)

2c_britneyly
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am

Re: Negative and Positive values of delta H and w

Postby 2c_britneyly » Mon Feb 18, 2019 4:01 pm

The sign of enthalpy is determined with respect to the system. Therefore, when ΔH is negative, you know heat is decreasing with respect to the system. This is the conventional way of writing signs unless otherwise stated.

Pritish Patil 1K
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Joined: Fri Sep 28, 2018 12:24 am

Re: Negative and Positive values of delta H and w

Postby Pritish Patil 1K » Tue Mar 12, 2019 1:24 pm

Work greater than 0 means work is done on the system; work less than 0 means that work is done on the surroundings. deltaH greater than 0 means heat is flowing in the system and deltaH less than 0 means that heat is flowing out of the system (assuming constant pressure).


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