Which reaction will have a negative ∆H value

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Discussion Overview

The discussion revolves around identifying which chemical reaction will have a negative ∆H value, focusing on the stability of products versus reactants. Participants explore various reactions, their energy requirements, and the implications for enthalpy changes.

Discussion Character

  • Homework-related, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant suggests that negative ∆H indicates that the product is more stable, eliminating reactions A and C due to energy requirements for solid to gas transitions.
  • Another participant argues that reaction D makes sense, asserting that ionization always requires energy.
  • A participant questions whether reaction D is the correct answer, expressing confusion about chlorine and its state as a monatomic gas, and asks why it would release energy.
  • There is a clarification that diatomic molecules can dissociate at high temperatures, which requires significant energy.
  • One participant concludes that reaction D has a positive ∆H value and inquires if both reactions B and E have negative ∆H values due to the stability of their products.
  • Another participant reiterates the point about ionization requiring energy, suggesting that both B and E could have negative ∆H values.
  • A participant proposes that reaction A could be the answer since it does not involve ionization, while questioning the energy requirements for a particle transitioning to a gas.
  • One participant clarifies that reaction E is not an ionization process.
  • A participant acknowledges confusion regarding the definition of ionization, indicating a misunderstanding about its meaning in the context of the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the validity of reactions D, B, and E regarding their ∆H values, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

Participants reference various reactions and their energy requirements, but there are unresolved assumptions about the definitions of ionization and the conditions under which reactions occur.

TT0
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Homework Statement


Screen Shot 2016-07-04 at 2.14.39 PM.png

Homework Equations

The Attempt at a Solution


Negative ∆H means that the product is more stable. Change from solid to gas requires energy so cancel out A and C. Reaction D doesn't make sense. The products of reaction B and E are more stable than the reactant because there is a full shell so it seems to me both would have a ∆H value. Can someone tell me what am I missing?

Cheers!
 
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Reaction D does make a perfect sense.

Ionization always requires energy.
 
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I thought chlorine didn't monatomic gases. So are you saying D is the answer? If so, why does it release energy?

Thanks a lot
 
TT0 said:
I thought chlorine didn't monatomic gases.

Every diatomic molecule can be split (forced to dissociation) at temperatures high enough. It typically requires a lot of energy (hence the need for high temperatures).
 
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I see, so D has a positive ∆H value.

Would you say both B and E have negative ∆H as the products are more stable?

Cheers!
 
TT0 said:
Would you say both B and E have negative ∆H as the products are more stable?
Borek said:
Ionization always requires energy.
 
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So I guess A is the answer then? As it does not ionise. C is sublimation which requires energy. If A is the answer, isn't energy required for a particle to turn into a gas?

Thanks!
 
E is not ionization.
 
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I see. I got confused and forgot ionisation does not mean turning into an ion. Thanks a lot
 

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