Question
Which one of the following characteristics is associated with adsorption?
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ΔG, ΔH and ΔS all are negative
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ΔG and ΔH are negative but ΔS is positive
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ΔG and ΔS are negative but ΔH is positive
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ΔG is negative but ΔH and ΔS are positive
Solution
A.
ΔG, ΔH and ΔS all are negative
Adsorption is a spontaneous process that occurs with the release of energy and decrease in the entropy of the substance. For a spontaneous process, ΔG must be negative,
ΔG = ΔH - T ΔS
As the process is exothermic and randomness of the molecule (entropy) decreases hence both ΔH and ΔS will be negative as well.
