The following questions consist of two statements one labelled ASSERTI...
Explanation:
The given statement consists of two parts - Assertion (A) and Reason (R). Let's analyze each of them separately and then try to understand the relationship between them.
Assertion: Many endothermic reactions that are not spontaneous at room temperature become spontaneous at high temperature.
Reason: Enthalpy of reaction may change on changing temperature.
Analysis:
Firstly, let's understand the meaning of the two terms used in the assertion - endothermic reactions and spontaneous reactions.
Endothermic reactions are those reactions that absorb heat from their surroundings. In other words, they require energy input to occur. On the other hand, spontaneous reactions are those that occur on their own without any external energy input.
Now, coming to the assertion, it says that many endothermic reactions that are not spontaneous at room temperature become spontaneous at high temperature. This is because increasing the temperature of the reaction mixture provides the necessary activation energy required for the reaction to proceed.
The reason given for this assertion is that the enthalpy of reaction may change on changing temperature. Enthalpy is a thermodynamic property that represents the heat content of a system. It is given by the formula H = E + PV, where E is the internal energy of the system, P is the pressure, and V is the volume. Enthalpy is a state function, which means that its value depends only on the initial and final states of the system, regardless of the path taken to get there.
Now, the enthalpy change of a reaction is given by ∆H = H(final state) - H(initial state). If ∆H is negative, the reaction is exothermic (releases heat), and if ∆H is positive, the reaction is endothermic (absorbs heat). When the temperature of a reaction is increased, the enthalpy of the reactants increases, which may lead to a change in the sign of ∆H. This means that an endothermic reaction may become exothermic at high temperatures, thereby becoming spontaneous.
Relationship between Assertion and Reason:
The reason given for the assertion is correct and provides a scientific explanation for why many endothermic reactions become spontaneous at high temperatures. Hence, both A and R are true, and R is the correct explanation of A.
Conclusion:
To summarize, many endothermic reactions that are not spontaneous at room temperature become spontaneous at high temperature because increasing the temperature provides the necessary activation energy required for the reaction to proceed. This is because the enthalpy of the reactants may change on changing temperature, leading to a change in the sign of the enthalpy change of the reaction. The reason given for the assertion is correct and provides a scientific explanation for why this happens. Therefore, both A and R are true, and R is the correct explanation of A.
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