## reversing signs

Mallika Singh 1G
Posts: 99
Joined: Sat Aug 24, 2019 12:16 am

### reversing signs

for calculating enthalpy change, when do you need to reverse the sign of delta H?

Bilal Pandit 1J
Posts: 98
Joined: Wed Sep 11, 2019 12:16 am

### Re: reversing signs

You only need to reverse the sign for the delta H if you are measuring the change in enthalpy in the surroundings, so the actual system will be the opposite of that.

Sam McNeill 1E
Posts: 110
Joined: Sat Aug 24, 2019 12:17 am

### Re: reversing signs

If something is heating something, the q will be negative since it is releasing heat into its surroundings.

005162902
Posts: 102
Joined: Wed Sep 18, 2019 12:15 am

### Re: reversing signs

The sign of delta H depends on whether or not the reaction is exothermic or endothermic. If it is exothermic, delta H will be negative. If the reaction is endothermic delta H will be positive because heat will be added.

BCaballero_4F
Posts: 94
Joined: Wed Nov 14, 2018 12:22 am

### Re: reversing signs

Whether or not delta H is positive or negative depends on the reaction (if it is endothermic or exothermic)

Kishan Shah 2G
Posts: 132
Joined: Thu Jul 11, 2019 12:15 am

### Re: reversing signs

You can reverse the sign of enthalpy change when doing Hess's law and you are trying to determine the overall reaction by manipulating the equations.

Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

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