What is the Correct Molar Enthalpy of Reaction for NaOH + NH4Cl?

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In summary, the speaker is having trouble calculating the enthalpy for a chemical reaction involving NaOH and NH4Cl. They have obtained a net ionic equation and calculated the sum of products and reactants, which should result in -136.73 kJ/mol. However, their answer checker says it is incorrect and they are wondering where they went wrong. Another speaker suggests that the standard heat of formation for NH4+ ion should be taken into account. They also mention that the net ionic equation should only involve the formation of water with a heat of around -55 kJ/mol. However, the exact value may vary depending on the solubility of ammonium chloride.
  • #1
gstullo
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I'm having some trouble with getting the correct entahlpy for the rxn:

NaOH + NH4Cl --> NaCl + NH3 + H2O

I've gotten the net ionic to be:

OH + NH4 --> NH3 +H2O

individuals to be sum of products (-) sum of reactants:

(-80.83+-285.84)-(-229.94 (for OH) and NH4 doesn't show anyvalue in my book.

This comes out to -136.73 which according to the little answer checker I've got here, is wrong. Where am I amiss?

Can anyone shed some light?
 
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  • #2
The NH4+ ion has a standard heat of formation of -132.5 kJ/mol. Assuming everything else is right, that should do it.
 
  • #3
The net ionic equation should simply be the formation of water

[tex]H^+_{(aq)} + OH^-_{(aq)} \xrightarrow ~H_2O_{(l)} [/tex]
This should be around -55kJ/mol

although it actually depends on the solubility of ammonium chloride, I may be wrong.
 

FAQ: What is the Correct Molar Enthalpy of Reaction for NaOH + NH4Cl?

What is molar enthalpy of reactions?

Molar enthalpy of reactions is a measure of the amount of heat released or absorbed during a chemical reaction, per mole of reactant or product.

How is molar enthalpy of reactions calculated?

Molar enthalpy of reactions can be calculated by measuring the change in enthalpy of the reactants and products and then using the coefficients in the balanced chemical equation to determine the molar ratios.

What is the significance of molar enthalpy of reactions?

Molar enthalpy of reactions helps to determine the energy changes that occur during a chemical reaction, which is important in understanding the thermodynamics and kinetics of a reaction.

How does molar enthalpy of reactions relate to enthalpy of formation?

Molar enthalpy of reactions is closely related to enthalpy of formation, as it is the difference in enthalpy between the products and reactants at a specific temperature and pressure. It can be used to calculate the enthalpy of formation of a compound.

Can the molar enthalpy of reactions be negative?

Yes, the molar enthalpy of reactions can be negative if the reaction releases heat, indicating an exothermic reaction. On the other hand, a positive molar enthalpy of reactions indicates an endothermic reaction where heat is absorbed.

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