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Practice each question, then open the answer or worked solution.
The reaction between H2(g) and O2(g) is highly feasible yet allowing the gases to stand at room temperature in the same vessel does not lead to the formation of water. Explain.
According to Maxwell Boltzmann energy distribution curve when temperature T becomes T+10 degree Celsius then the effective collision and energy of molecules increases resulting in the formation of a product.
Why does the rate of a reaction increase with a rise in temperature?
Rate of reaction increases with the rise in temperature because at the higher temperature the fraction of particles collision to cross the energy barrier will be large. Therefore the rate also becomes faster.
Oxygen is available in plenty in the air yet fuels do not burn by themselves at room temperature. Explain.
Oxygen is available in plenty of air yet fuels do not burn by themselves at room temperature because reactants must have a minimum amount of energy known as the activation energy to form a product.
Why is the probability of reaction with molecularity higher than three very rare?
For a reaction having more than three molecules, the proper orientation is not possible that makes these reactions rare. Therefore the probability of more than three molecules colliding simultaneously will be small.
Why does the rate of any reaction generally decrease during the reaction?
The rate of a reaction decreases because the reactants will proceed to convert into the products. The rate of a reaction always depends on the concentration of the reactants.
Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction. Explain with the help of one example.
Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction because for a reaction to occur it is important for the molecules to have an energy greater than the activation energy.
For example,
Diamond → Graphite ΔG= -ve
ΔG negative means that the reaction is feasible but this reaction is a slow process as energy is less than the activation energy.
Why in the redox titration of KMnO4vs oxalic acid, we heat oxalic acid solution before starting the titration?
We heat oxalic acid solution because without heating it is a slow process as energy greater than the activation energy is required for a reaction. So to increase the energy, the temperature must be increased which is only possible by heating the oxalic acid solution.
Why can’t molecularity of any reaction be equal to zero?
Zero molecularity means there is no reactant, as a result of which a reaction cannot occur. So if there is a reaction then its molecularity will be greater than zero.
Why is molecularity applicable only to elementary reactions and order is applicable for elementary as well as complex reactions?
Molecularity is applicable only for elementary reactions as they are the single-step reactions and the rate depends on the concentration of each molecule, whereas in case of complex reactions there are multiple reactions involved and thus molecularity holds no meaning.
Why can we not determine the order of a reaction by taking into consideration the balanced chemical equation?
Order is an experimental quantity. For example, in complex reactions, the rate and order are dependent on the slow step reactions, so in such cases, the order is not completely dependent on the balanced chemical equations. We cannot determine the order by taking into consideration the balanced chemical equation.
Class 12 Chemistry NCERT Exemplar Problems on Chemical KineticsChemical kinetics is the study and discussion of chemical reactions with respect to reaction rates, the effect of various variables, the formation of intermediates and the re-arrangement of atoms. Solve the NCERT Exemplar Class 12 Chemistry Chapter 4 Chemical Kinetics for a better understanding of the chapter. Chemical kinetics is a fundamental topic which is important for the Class 12 board examination.