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Nitrogen oxides are commonly found in the atmosphere in areas where there is serious atmospheric pollution - VCE - SSCE Chemistry - Question 5 - 2011 - Paper 1
Question 5
Nitrogen oxides are commonly found in the atmosphere in areas where there is serious atmospheric pollution. Nitrogen monoxide, NO, is generated from the reaction bet... show full transcript
Worked Solution & Example Answer:Nitrogen oxides are commonly found in the atmosphere in areas where there is serious atmospheric pollution - VCE - SSCE Chemistry - Question 5 - 2011 - Paper 1
Step 1
Explain why the rate of the reaction $N_2(g) + O_2(g) \rightarrow 2NO(g)$ will never be greater than the rate of the reaction $2NO(g) \rightleftharpoons N_2(g) + O_2(g)$ while the system is reaching equilibrium.
Answer
The rates of the forward and reverse reactions approach equilibrium at different rates. As the system approaches equilibrium, the rate of the forward reaction (producing NO) will begin to decrease due to the depletion of the reactants, while the rate of the reverse reaction (producing N2 and O2) will increase as the concentration of NO rises. Once equilibrium is reached, the rates of both reactions will become equal, meaning the rate of the forward reaction can never exceed that of the reverse reaction as the system stabilizes.
Step 2
Explain why combustion engines are such good chemical environments for the production of NO(g).
Answer
Combustion engines create high temperatures and pressures, which are conducive to the formation of nitrogen oxides like NO. At these elevated temperatures, the activation energy for the reaction between nitrogen and oxygen is significantly lowered, facilitating the reaction. Additionally, the turbulent flow and high-energy collisions in combustion engines increase the chances of nitrogen and oxygen molecules overcoming the activation barrier, leading to a more efficient production of NO.
Step 3
Sketch, on the axes provided below, a fully labelled energy profile diagram for the decomposition reaction of NO. Indicate on the diagram the effect of using a catalyst in this reaction.
Answer
A properly labelled energy profile diagram would show the energy of reactants and products with a peak denoting the activated complex. When a catalyst is introduced, the height of the peak decreases, indicating a lower activation energy. This allows the reaction to proceed faster without affecting the energy of the reactants or products. The diagram should include axes labelled 'enthalpy' on the vertical axis and 'time' on the horizontal axis, with curves for uncatalyzed and catalyzed reactions.