Enthelpy change and activation energy

In summary: Can you please let me know if I am on the right track or if I need to do more research? Thanks!In summary, the value of the enthalpy change for reaction 2NO(g) + O2(g) 2NO2(g) is -115 kJ mol-1 and the activation energy for the forward reaction is reported as negative.
  • #1
newkidintownu
5
0
Please can someone help.

I am having trouble with the following question involving the production of nitric acid:

What is the value for the enthaply change for reaction 2NO(g) + O2(g) 2NO2(g)

and what is the activation energy for the forward reaction.

I think the answer for the value of the enthalpy change is ΔH = -115 kJ mol-1 but am not sure.

Could someone let me know if this is correct and help with the activation energy bit.

Thanks

Ann
 
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  • #2
Nitric acid?? Nitrogen dioxide.

Your enthalpy for 2NO + O2 ---> 2NO2 looks plausible to me. This is a third order reaction and seems to involve a pre-equilibrium
NO + O2 ---> NO3 followed by a collision of the latter with
NO to form the nitrogen dioxide. The activation energy is reported as negative:
E = -1.1 Kcal/mole (Benson, "The Foundations of Chemical Kinetics", McGraw-Hill, 1960) as
measured by M. Bodenstein (Helv. Chim. Acta, 18, 743 (1935). Maybe this work is not the last word on this reaction, in which case you'll need to do some research in the library.
 
  • #3
newkidintownu said:
Please can someone help.

I am having trouble with the following question involving the production of nitric acid:

What is the value for the enthaply change for reaction 2NO(g) + O2(g) 2NO2(g)

and what is the activation energy for the forward reaction.

I think the answer for the value of the enthalpy change is ΔH = -115 kJ mol-1 but am not sure.

Could someone let me know if this is correct and help with the activation energy bit.

Thanks

Ann
[tex]2NO + O_2 --> 2NO_2[/tex]

[tex]\Delta H^0_f (NO) = +\ 90.29\ kJ\ mol^{-1}:[/tex]
http://webbook.nist.gov/cgi/cbook.cgi?Formula=NO&NoIon=on&Units=SI&cTG=on

[tex]\Delta H^0_f (NO_2) = +\ 33.10\ kJ\ mol^{-1}:[/tex]
http://webbook.nist.gov/cgi/cbook.cgi?Formula=NO2&NoIon=on&Units=SI&cTG=on

So:
[tex]\Delta H^0_{reaction} = 2\cdot 33.10\ -\ 2\cdot 90.29 =\ -\ 114.38\ kJ\ mol^{-1}[/tex]
 
Last edited:
  • #4
the kinetic of the following reaction

:)
Hello, I am carrying a study on a column absorption of nitric acid, but I did not find the kinetic of the following reaction:
2NO2 <-------> N2O4
3NO2+H2O <----> 2HNO3+NO
3HNO2+H2O <-----> ZABHNO3+2NO
and 3HNO2+H2O <-----> HNO3+2NO
thinks
 

1. What is enthalpy change?

Enthalpy change is the difference in energy between the reactants and products of a chemical reaction. It can be either endothermic (absorbing heat) or exothermic (releasing heat).

2. How is enthalpy change measured?

Enthalpy change is usually measured in joules (J) or kilojoules (kJ). It can be calculated using the heat released or absorbed during a reaction, as well as the change in temperature and mass of the reactants and products.

3. What is activation energy?

Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is the energy needed to break the bonds of the reactants and initiate the reaction.

4. How does activation energy affect the rate of a reaction?

The higher the activation energy, the slower the rate of the reaction. This is because a higher amount of energy is needed to overcome the energy barrier and initiate the reaction. Conversely, a lower activation energy means the reaction can occur more quickly.

5. How can activation energy be reduced?

Activation energy can be reduced by using a catalyst, which lowers the energy barrier for the reaction to occur. This allows the reaction to proceed at a faster rate and with less energy input. Alternatively, increasing the temperature can also lower the activation energy by providing more energy for the reactant molecules to collide and react.

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