Test: 35 Year JEE Previous Year Questions: The Solid State & Surface Chemistry

It is zero order reaction
[NOTE : Adsorption of gas on metal surface is of zero
order]

In bcc - points are at corners and one in the centre of the unit cell.
Number of atoms per unit cell = 

In fcc - points are at the corners and also centre of the six faces of each cell.
Number of atoms per unit cell = 

Since in NaCl type of structure 4 formula units form a cell. Number of formulas in cube shaped crystals

No. of unit cells present in a cubic crystal =

∴ units cells =    unit cells.

As adsorption is an exothermic process.
∴ Rise in temperature will decrease adsorption
(according to Le-chatelier principle).

When equal number of cations and anions are missing from their regular lattice positions, we have schottky defect.
This type of defects are more common in ionic
compounds with high co-ordination number and where the size of positive and negative ions are almost equal
e.g. NaCl KCl etc.

Enzymes are very specific biological catalysts
possessing well - defined active sites

Number of A ions in the unit cell =

Number of B ions in the unit cell =

Hence empirical formula of the compound = AB₃

Particle size of colloidal particle = 1mμ to 100 mμ      (suppose 10 mμ)

Particle size of true solution particle = 1mm

When oppositely charged sols are mixed their charges are neutralised. Both sols may be partially or completely precipitated.

The face centered cubic unit cell contains 4 atom
∴ Total volume of atoms = 

According to Langmuir's Model of adsorption of a gas on a soild surface the mass of gas adsorbed(x)per gram of the adsorbent (m) is directly proportional to the pressure of the gas (p) at constant temperature i.e.

From the given data, we have
Number of Y atoms in a unit cell = 4
Number of X atoms in a unit cell = 

From the above we get the formula of the compound as
X_{16 / 3} Y₄ or X₄Y₃

For a protective colloid μ lesser the value of gold number better is the protective power.
Thus the correct order of protective power of A, B, C and D is

Hence (c) is the correct answer

Adsorption is an exothermic process, hence DH will always be negative

For fcc unit cell, 

For an Fcc crystal 

Packing fraction is defined as the ratio of the volume of the unit cell that is occupied by the spheres to the volume of the unit cell.
P.F. for cpp and bcc are 0.74 and 0.68 respectively.
So, the free space in ccp and bcc are 26% & 32% respectively.

No. of atoms in the corners (A)  = 

No. of atoms at face centres (B) = 

∴ Formula is = AB_2.5 or A₂B₅

For BCC structure 

The Freundlich adsorption isotherm is mathematically represented as 

Among the given crystals only silicon is as a covalent solid.

According to Hardly Schulze rule, greater the charge on cation, greater is its coagulating power for negatively charged solution. hence the correct order of coagulating power : Na⁺ < Ba²⁺ < Al³⁺

Relation between radius of cation, anion and edge length of the cube

In bcc the atoms touch along body diagonal 

Let the weight of acetic acid initially be w₁ in 50 ml of 0.060 N solution

Let the N =  (Normality = 0.06 N)

After an hour, the strength of acetic acid = 0.042 N
so, let the weight of acetic acid be w₂

⇒ w₂ = 0.126 g = 126 mg
So amount of acetic acid adsorbed per 3g
= 180 – 126 mg = 54 mg
Amount of acetic acid adsorbed per g
= 54/3 = 18 mg

According to Freundlich adsorption isotherm 

Thus if a graph is plotted between log (x/m) and log P, a straight line will be obtained

The slope of the line is equal to 1/n and the intercept on log x/m axis will correspond to log K.