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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: joyabraham on August 07, 2021, 06:59:40 AM

Title: Heat of reaction
Post by: joyabraham on August 07, 2021, 06:59:40 AM

How much is the heat of reaction for AlF3 + 3H2O «→» Al(OH)3 + 3HF

Title: Re: Heat of reaction
Post by: Borek on August 07, 2021, 09:20:25 AM

Please read the forum rules (https://www.chemicalforums.com/index.php?topic=65859.0). You have to show your attempts at answering the question/solving the problem to receive help, it is a forum policy.

Title: Re: Heat of reaction
Post by: joyabraham on August 08, 2021, 03:25:53 AM

I checked many websites but could not find the answer or guidance. One website has a calculator, but unfortunately it has no AlF3 in the list of reactants to choose from.

Title: Re: Heat of reaction
Post by: Borek on August 08, 2021, 03:38:57 AM

Just use the Hess's law, enthalpies of formation of all compounds listed are trivial to find.

Title: Re: Heat of reaction
Post by: joyabraham on August 08, 2021, 03:54:17 AM

I am unable to calculate using Hess or other chemistry laws and unable to find the answer (the number) from internet, hence asked this help.

Title: Re: Heat of reaction
Post by: Orcio_87 on August 08, 2021, 11:02:08 AM

Quote

I am unable to calculate using Hess or other chemistry laws

Hess law states that enthalpy of the reaction is equal enthalpy of products minus enthalpy of reagents.

Title: Re: Heat of reaction
Post by: joyabraham on August 09, 2021, 01:50:56 AM

Thank you for the advice. Enthalpy of Al(OH)3 is not found in any site in internet. If anybody has the answer to my question for this reaction AlF3 (l) + 3H2O (g)→ Al(OH)3 (l) + 3HF (g) kindly give. Whatever guidance provided by earlier replies did not help.

Title: Re: Heat of reaction
Post by: Borek on August 09, 2021, 02:49:57 AM

Quote from: joyabraham on August 09, 2021, 01:50:56 AM

Enthalpy of Al(OH)3 is not found in any site in internet.

Googling for "Aluminum hydroxide enthalpy of formation" got me the answer in no time.

Title: Re: Heat of reaction
Post by: joyabraham on August 09, 2021, 03:19:51 AM

Does anybody know if this is an exothermic or endothermic reaction?

Title: Re: Heat of reaction
Post by: Orcio_87 on August 09, 2021, 03:22:30 AM

True, but joyabraham asks for a liquid (melted) AlF₃ and Al(OH)₃, so this requires additional data to find (heat capacities and enthalpies of melting).

Title: Re: Heat of reaction
Post by: Corribus on August 09, 2021, 08:53:10 AM

Heat of formation for liquid AlF3 can be found here.

https://webbook.nist.gov/cgi/cbook.cgi?ID=C7784181&Units=SI&Mask=2#Thermo-Condensed

Usual procedure is to assume these values are invariant over temperature. And in any case the temperature isn't specified, so high precision isn't possible anyway.

Come on, this is just laziness.