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: If hydrogen and oxygen are mixed and kept in the same vessel at room temperature, the reaction does not take place to form water because:
A.Activation energy for the reaction is very high at room temperature.
B.Molecules have no proper orientation to react to form water
C.The frequency of collisions is not high enough for the reaction to take place.
D.No catalyst is present in the reaction mixture.

Last updated date: 20th Jun 2024
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Hint:There are some reactions which need energy to start the reactions, those reactions require activation energy. This energy is required to move from energy level of reactants to energy level of transition state.

Complete answer:
Activation Energy: Activation energy is defined as energy required to cross the potential barrier to form the product. It is denoted by $E {{a} {{}}} $
Complete step by step solution: As we know that hydrogen and oxygen reactions form water and the reactions between the hydrogen and oxygen is highly exothermic i.e. produces large amounts of energy.
${{H}_{2}}+\dfrac{1}{2}{{O}_{2}}\to {{H}_{2}}O + Heat$
But when hydrogen and oxygen mixes at room temperature there are no reactions taking place because some minimum amount of energy is required to start the reaction i.e. activation energy is required. So, the reaction will not occur at room temperature.
Activation energy can be calculated using a rate constant and temperature graph. When the natural log of rate constant is plotted against the inverse of temperature then from the slope of this graph we can calculate activation energy.

Therefore, the option-A is correct.

The concept of activation energy must be clear and why reaction needs activation energy. Activation energy is measured in joules per mole. Activation energies are quite important because if they were not there then unwanted reactions would also have taken place irrespective of their requirement. This energy is always positive. Activation energy helps in overcoming the force of repulsion thereby breaking bonds and helps transforming reactants into products.