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Topic: Enthalpy value of Decomposition of NaHCO3  (Read 10343 times)

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Offline Google1036

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Enthalpy value of Decomposition of NaHCO3
« on: September 08, 2007, 11:33:15 PM »
Hello, anyone know the theoretical value for the enthalpy change of the reaction:

2 NaHCO3  → Na2CO3   + H2O  + CO2

Thnk y in advance..
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Offline Quantum07

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Re: Enthalpy value of Decomposition of NaHCO3
« Reply #1 on: September 14, 2007, 06:44:27 PM »
You need to look at the Enthalpy values in the back of your chemistry book under the Thermodynamic Index.

From these values you calculate the enthalpy change for the reaction given by the formula:

n(Enthalpy of products) - n(Enthalpy of reactants) = Enthalpy of reaction

n represets the moles of each reactant or product in this case it is 1 for all the products and 2 for the reactants.

So for your case it would be

(Enthalpy for Na2CO3 + enthalpy for H2O + enthalpy CO2) -  2x(enthalpy for NaHCO3)
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Offline constant thinker

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Re: Enthalpy value of Decomposition of NaHCO3
« Reply #2 on: September 14, 2007, 07:58:36 PM »
Another way would be to use Hess's Law.

Actually now that I looked at it Quantum07 basically did that.

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Offline Quantum07

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Re: Enthalpy value of Decomposition of NaHCO3
« Reply #3 on: September 15, 2007, 04:44:42 PM »
What I did was not HESS'S LAW. Hess's Law is used to calculate the change in enthalpy, entropy, or Gibb's Free Energy from known reactions.

What I did was simply find the enthalpy change from the enthalpy values in the thermodynamic index of a chemistry book.

They aren't the same thing.
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