2 NO(g) + O2(g) → 2 NO2(g)
A student investigates the reactions of nitrogen oxides. One of the reactions in the investigation requires an equimolar mixture of NO(g) and NO2(g) , which the student produces by using the reaction represented above.
The particle-level representation of the equimolar mixture of NO(g) and NO2(g) in the flask at the completion of the reaction between NO(g) and O2(g) is shown below in the box on the right. In the box below on the left, draw the particle-level representation of the reactant mixture of NO(g) and O2(g) that would yield the product mixture shown in the box on the right. In your drawing, represent oxygen atoms and nitrogen atoms as indicated below.
The student reads in a reference text that NO(g) and NO2(g) will react as represented by the equation below. Thermodynamic data for the reaction are given in the table below the equation.
NO(g) + NO2(g) N2O3(g)
ΔH°298 |
ΔS°298 |
ΔG°298 |
− 40.4 kJ/molrxn |
−138.5 J/(K ⋅ molrxn) |
0.87 kJ/molrxn |
The student begins with an equimolar mixture of NO(g) and NO2(g) in a rigid reaction vessel and the mixture reaches equilibrium at 298 K.
The student hypothesizes that increasing the temperature will increase the amount of N2O3(g) in the equilibrium mixture. Indicate whether you agree or disagree with the hypothesis. Justify your answer.
N2O3(g) reacts with water to form nitrous acid, HNO2(aq), a compound involved in the production of acid rain. The reaction is represented below.
N2O3(g) + H2O(l) → 2 HNO2(aq)
The skeletal structure of the HNO2 molecule is shown in the box below.
H O N O |
- To produce an aqueous solution of HNO2 , the student bubbles N2O3(g) into distilled water. Assume that the reaction goes to completion and that HNO2 is the only species produced. To determine the concentration of HNO2(aq) in the resulting solution, the student titrates a 100. mL sample of the solution with 0.100 M KOH(aq). The neutralization reaction is represented below.
HNO2(aq) + OH− (aq) → NO2−(aq) + H2O(l)
The following titration curve shows the change in pH of the solution during the titration.
Use the titration curve and the information above to
During the titration, after a volume of 15 mL of 0.100 M KOH(aq) has been added , which species, HNO2(aq) or NO2–(aq) , is present at a higher concentration in the solution? Justify your answer.
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