Chemistry -rates of reaction-catalysts and activation energy-exercises

Catalysts and activation energy exercises
On the right is an energy profile of an exothermic reaction in the absence of a catalyst. Discuss the changes that occur to this profile when a catalyst is added. Solution
The diagram on the right shows the distribution of kinetic energies of particles at a given temperature. The shaded area indicates the particles with sufficient energy to break bonds and initiate the reaction. Explain how this diagram changes when a catalyst is added. Solution
Draw the energy profile of an endothermic reaction and explain how the addition of a catalyst changes the energy profile.
A pressure cooker is used to significantly reduce the time of cooking. At high pressure water boils at a temperature greater than 100 ^oC. Explain how a pressure cooker decreases the time it takes to cook a meal.
Nitrogen reacts with oxygen according to the equation below. N_2(g) + 2O_2(g) <=> 2NO_2(g) The reaction is endothermic requiring 63kJ per mol of nitrogen gas. Draw an energy profile on the set of axis on the right. Label products, reactants, change in enthalpy, activation energy. Give a reason why the reaction proceeds very slowly at room temperature. Solution Give a reason why the reaction proceeds even faster when the catalyst is finely ground. Hide solution The activation energy for the reaction is very high. This is due to the fact that it is very difficult to break the triple bond of the nitrogen molecule and the double bond of the oxygen molecule.
The rate of a reaction can be increased by an increase in temperature and or the addition of a catalyst. Discuss the similarities and differences in the way a catalyst and an input of heat energy incerease the rate of the reaciton.
A student was heard to say "When you heat up a reaction vessel you lower the activation energy and so increase the rate of the reaction" . Do you agree? Explain