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1. Calculate the enthalpy of reaction for the reaction of nitrogen dioxide with

ID: 704518 • Letter: 1

Question

1. Calculate the enthalpy of reaction for the reaction of nitrogen dioxide with water represented by the following equation:

3 NO2(g) + H2O(l) ?2 HNO3(aq) + NO(g)    ?rH=?

Use the following information to answer Question 1

Given the following reactions:

Reaction I           

2 NO(g) + O2(g) ?2 NO2(g)                                   ?rH = -173 kJ

Reaction II         

2 N2(g) + 5 O2(g) + 2 H2O(l)?4 HNO3(aq)            ?rH = -255 kJ

Reaction III        

N2(g) + O2(g) ?2 NO(g)                                         ?rH= +181 kJ

2. Calculate the enthalpy of reaction for the reaction of nitrogen dioxide with water represented by the following equation:

3 NO2(g) + H2O(l) ?2 HNO3(aq) + NO(g)    ?rH=?

Given the following reactions:

Reaction I           

2 NO(g) + O2(g) ?2 NO2(g)                                   ?rH = -173 kJ

Reaction II         

2 N2(g) + 5 O2(g) + 2 H2O(l)?4 HNO3(aq)            ?rH = -255 kJ

Reaction III        

N2(g) + O2(g) ?2 NO(g)                                         ?rH= +181 kJ

Explanation / Answer

Ans :

The enthalpy of the desired reaction can be determined usinh Hess's law.

The desired reaction can be obtained by :

= (reverse of 1.5 times of reaction 1) + ( half of reaction 2 ) + (reverse of reaction 3)

So the enthalpy of the desired reaction = (173 x 1.5) + (-255/2) + (-181)

= -49 KJ