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Rate of physisorption increases with:
Physisorption is exothermic in nature. Therefore in accordance with Le-Chatliers principle, it decreases with increase in temperature. This means physisorption occurs at a low temperature more readily.
Adsorption is accompanied with:
Adsorption is accompanied with decrease in entropy and enthalpy of system. The value of TΔS is negative.
Adsorption decreases randomness and thus, ΔS=−ve and also, TΔS = −ve.
Which statement is not correct:
For adsorption of gas on solid surface, the plots of log x/m vs. log P is linear with a slope equal to:
For the adsorption of a gas on a solid x/m = kp1/n. This equation is known as Freundlich Adsorption Isotherm.
On taking logarithm on both sides, we obtain, logx/m = logk+ 1/nlogp
∴ plot of log(x/m) versus log p will be linear with slope = 1/n .
Which is correct in case of van der Waals’ adsorption:
If the accumulation of gas on the surface of a solid occurs on account of weak van der Waals’ forces, the adsorption is termed as physical adsorption or physisorption.
Hence, Physisorption can also be called as Van der Waals adsorption.
Physical adsorption of a gas by a solid is generally reversible. We can say by Le-Chatelier's principle that more of gas is adsorbed when pressure is increased as the volume of the gas decreases and since the adsorption process is exothermic, the physical adsorption occurs readily at low temperature and decreases with increasing temperature.
So the correct case is when it is Low temperature and high pressure the Physisorption tends to happen.
According to Langmuir adsorption isotherm the amount of gas adsorbed at very high pressure:
According to Langmuir Adsorption isotherm, the amount of gas adsorbed at very high pressures reaches a constant limiting value. The amount of gas adsorbed will not increase with the further increase in pressure
Which characteristic is not correct for physical adsorption:
Adsorption of a gas on solid metal surface is spontaneous and exothermic, then:
Surface area available for adsorption per g of catalyst is called:
Surface area available for adsorption per gram of catalyst is called specific surface area.
Specific surface area is important to measure to evaluate the activity and adsorption capacity of materials. (e.g. catalysis and adsorbent).
The specific surface area is increased as the particle size becomes small. The specific surface area is also increased if the particle has pores. The surface activity and adsorption volume are changed according to the specific surface area.
Plots of log vs. log C showing a straight line parallel to X-axis reveals that:
The Langmuir adsorption isotherm is deduced using the assumption:
The Langmuir adsorption isotherm is deduced using the assumption that the adsorption sites are equivalent in their ability to absorb the particles.
Langmuir adsorption isotherm shows the following characteristics:
Adsorption of methane follows the Langmuir adsorption isotherm at 90K. If p = 1.896cm3g-1bar-1 and b = 0.146bar-1. Calculate the value of θ.
p = 1.896cm3g-1 bar-1
b = 0.146 bar-1
Substitute in the corresponding equation