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Standard XII
Chemistry
Entropy
Why are exoth...
Question

Why are exothermic reactions said to have a negative enthalpy?

A
Because energy is flowing from the system to the environment.
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B
Because energy is flowing from the environment into a closed system.
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C
Because endergonic reactions like ATP→ADP have a negative change in free energy.
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D
Because the movement of energy is based on the direction it is flowing.
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Solution

The correct option is C Because energy is flowing from the system to the environment.
Explained Above.

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Q. For a chemical reactions, the free energy change (ΔG) is negative. The reaction is
Q. Statement 1: An exothermic reaction has a negative value of △H.
Statement 2 : In an exothermic reaction the products have less potential energy than the reactants.
Q. Statement 1: A spontaneous reaction is always exothermic.
Statement 2: Exothermic reactions release energy from the system.
Q. The free energy change accompanying a reaction is negative.
Which of the following options is the correct option?
Q. Free energy, G=H−TΔS, is a state function that indicates whether a reaction is spontaneous or non-spontaneous. If you think of TS as the part of the system`s energy that is disordered already, then (H−TS) is the part of the system`s energy that is still ordered and therefore free to cause spontaneous change by becoming disordered.
Also, ΔG=ΔH−TΔS

From the second law of Thermodynamics, a reaction is spontaneous if ΔtotalS is positive, non-spontaneous if ΔtotalS is negative, and at equilibrium if ΔtotalS is zero.

Since, −TΔS=ΔG and since ΔG and ΔS have opposite signs, we can restate the Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure.
If ΔG<0, the reaction is spontaneous
If ΔG>0, the reaction is non-spontaneous
If ΔG=0, the reaction is at equilibrium

Read the above paragraph carefully and answer the following questions based on the above comprehension.

A particular reaction has a negative value for the free energy change. Then at ordinary temperature:

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