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Which statement is correct when adsorpti...

Which statement is correct when adsorption of gas take place on metal surface?
(a) `delta H` becomes less negative with pregress of reaction.
(b) with progress of reaction the strength of residual forces increases.
(c) `NH_3` is adsorbed more than `N_2`.
(d) Equilibrium concentration of adsorbate increases with increase in temperature.

A

a,c

B

a,b

C

b,d

D

b,c

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question regarding the correct statement when gas adsorption occurs on a metal surface, we will analyze each option step by step. ### Step 1: Analyze Statement (a) **Statement (a):** `ΔH` becomes less negative with the progress of the reaction. - When a gas is adsorbed onto a metal surface, the randomness (entropy, ΔS) of the system decreases because the gas molecules become more ordered when they adhere to the surface. - Since ΔG = ΔH - TΔS, a decrease in ΔS (which is negative) leads to an increase in ΔH (making it less negative). - Therefore, this statement is **correct**. ### Step 2: Analyze Statement (b) **Statement (b):** With the progress of the reaction, the strength of residual forces increases. - Residual forces refer to the unbalanced forces acting on the adsorbed molecules. - As more gas molecules adsorb onto the surface, the forces acting on each molecule become more balanced, leading to a decrease in residual forces. - Thus, this statement is **incorrect**. ### Step 3: Analyze Statement (c) **Statement (c):** `NH3` is adsorbed more than `N2`. - `NH3` is a polar molecule, while `N2` is a non-polar molecule. - Polar molecules generally have stronger interactions with surfaces than non-polar molecules, leading to a higher rate of adsorption. - Therefore, this statement is **correct**. ### Step 4: Analyze Statement (d) **Statement (d):** Equilibrium concentration of adsorbate increases with an increase in temperature. - Adsorption is typically exothermic and decreases with an increase in temperature according to Le Chatelier's principle. - Therefore, if temperature increases, the equilibrium concentration of the adsorbate will decrease. - Thus, this statement is **incorrect**. ### Conclusion The correct statements are (a) and (c). ### Final Answer The correct options are (a) and (c). ---
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