Let [A₀] = 100;
When t = t_99.9%; [A] = (100-99.9) = 0.1
\(k=\frac { 2.303 }{ t } \log\left( \frac { [{ A }_{ 0 }] }{ [A] } \right) \)
\({ t }_{ 99.9\% }=\frac { 2.303 }{ K } \log\left( \frac { 100 }{ 0.1 } \right) \)
\({ t }_{ 99.9\% }=\frac { 2.303 }{ K } \log1000\)
\({ t }_{ 99.9\% }=\frac { 2.303 }{ K } (3)\)
\({ t }_{ 99.9\% }=\frac { 6.909 }{ K } \)
\({ t }_{ 99.9\% }=10\times \frac { 0.69 }{ K } \)
\({ t }_{ 99.9\% }={ 10 } t_{ 1/2 }\)

(i) Diborane is used as a high energy fuel for propellant.
(ii) It is used as a reducing agent in organic chemistry.
(iii) It is used in welding torches.

(i) Calcination is the process in which the concentrated ore is strongly heated in the absence of air.
(ii)  During this process, the water of crystallisation present in the hydrated oxide escapes as moisture.
(iii) Any organic matter (if present) also get expelled leaving behind a porous ore.
(iv) This method can also be carried out with 4 limited supply of air.
(v) During calcination of carbonate ore carbon dioxide is expelled.
\(Pb{ CO }_{ 2 }\overset { \Delta }{ \longrightarrow } PbO+{ CO }_{ 2 }\uparrow \)

Mond process for refining nickel:
The impure nickel is heated in a stream of carbon monoxide at around 350 K. The nickel reacts with the CO to form a highly volatile nickel tetracarbonyl. The solid impurities are left behind. 
\(\mathrm{Ni}_{(\mathrm{s})}+4 \mathrm{CO}_{(\mathrm{g})}\ \rightarrow \ \left[\mathrm{Ni}(\mathrm{CO})_{4}\right]_{(g)}\)
(ii) When the Nickel Carbonyl Complex is heated at 460 K, it decomposes to give pure nickel.
\(\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]_{(g)} \stackrel{460 \mathrm{~K}}{\longrightarrow} \mathrm{Ni}_{(s)(\text { pure })}+4 \mathrm{CO}_{(\mathrm{g})}\)

Rate of a reaction at any time depends on the concentration of the reactants which keeps on decreasing with time.

Distillation, liquation, electrolytic refining, zone refining, vapour phase method, van -Arkel method

Number of X type atoms in the unit cell \(=8 \times \frac{1}{8}=1\)
Number of Y type atoms in the unit cell \(=1 \times \frac{1}{1}=1\)
Hence the formula is XY (or) X₁Y₁

The structural units of an ionic crystal are cations and anions. They are bound together by strong electrostatic attractive forces. To maximize the attractive force, cations are surrounded by as many anions as possible and vice versa. Hence they are hard and brittle.

Oxides of Carbon	Structure	Parameters
CO		Three electron pairs are shared between carbon and oxygen. The C-O bond distance is 1.128\(\overset{o}{A}\).
CO2		Equal bond distance for the both C-O bonds. Two C-O sigma bond, It has 3c-4e bond.

1. This process is called as Hall-Heroult process.
Cathode: In this method, electrolysis is carried out in an iron tank lined with carbon which acts as the cathode.
Anode: The carbon blocks immersed in the electrolyte acts as a anode.
Eletrolyte: A 20% solution of alumina, obtained from the bauxite ore is mixed with molten Cryolite and is taken in the electrolysis chamber.
2. About 10% calcium chloride is also added to the solution.
3. Here Calcium chloride helps to lower the melting point of the mixture.
Temperature: The fused mixture is maintained at a temperature of above 1270 K.
4. The chemical reactions involved in this process as follows
(a) Ionisaiton of alumina: \({ A }l_{ 2 }{ O }_{ 3 }\longrightarrow { 2Al }^{ 3+ }+{ 3O }^{ 2- }\)
(b) Reaction at cathode: \(2{ Al }^{ 3+ }_{(melt)}+{ 6e }^{ - }\longrightarrow { Al }_{ (l) }\)
(c) Reaction at anode: \(6{ O }^{2-}_{(melt)}\longrightarrow { 3O }_{ 2 }+{ 12e }^{ - }\)
5. Since carbon acts as anode the following reaction also takes place
(a) \({ C }_{ (s) }+{ O }^{ 2- }_{(melt)}\longrightarrow CO+{ 2e }^{ - }\)
(b) \({ C }_{ (s) }+{ 2O }^{ 2- }_{(melt)}\longrightarrow { CO }_{ 2 }+{ 4e }^{ - }\)
6. Due to the above two reactions, anodes are slowly consumed during the electrolysis.
7. The pure aluminium is formed at the cathode. The net electrolysis reaction can be written as
\({ 4Al }^{ 3+ }_{(melt)}+{ 6O }^{ 2- }_{(melt)}+{ 3C }_{ (s) }\longrightarrow { 4Al }_{ (l) }+{ 3CO }_{ 2(g) }\)

Given data: Rate = 5.2 x 10^-6 mol lit^-1 sec^-1
Initial concentration [A] = 2.6 x 10^-3
Formula: Rate = k[A]¹
Solution: Rate = 5.2 x 10^-6 mol lit^-1 sec^-1 = k x 2.6 x 10^-3 lit^-1
= \(\frac { 5.26\times { 10 }^{ -6 }mol{ \ lit }^{ -1 }{ sec }^{ -1 } }{ 2.6\times { 10 }^{ -3 }mol \ { lit }^{ -1 } } \)= 2 x 10^-3
∴ k = 2 x 10^-3 s^-1

Schottky defect:
(i) Schottky defect arises due to the missing of equal number of cations and anions from the crystal lattice.
(ii) This effect does not change the stoichiometry of the crystal.
(iii) Ionic solids in which the cation and anion are of almost of similar size show schottky defect. Ex: NaCl.
(iv) Presence of large number of schottky defects in a crystal, lowers its density.

Frenkel defect:
(i) Frenkel defect arises due to the dislocation of ions from its crystal lattice.
(ii) The ion which is missing from the lattice point occupies an interstitial position.
(iii) This defect is shown by ionic solids in which cation and anion differ in size.
(iv) Unlike Schottky defect, this defect does not affect the density of the crystal.
(v) For example AgBr, in this case, small Ag⁺ ion leaves its normal site and occupies an interstitial position.

(a) Elementary reaction
Each and Every single step in a reaction mechanism is called an elementary reaction.
Rate = k[A] [B]
(b)

Order of reaction	Molecularity of a reaction
Order of reaction is the sum of the powers of concentration terms involved in the experimentally determined rate law.	Molecularity of a reaction is the total number of reactant species that are involved in an elementary step.
It can be zero (or) fractional (or) integer	It is always a whole number, cannot be zero or a fractional number.
It is assigned for a overall reaction.	It is assigned for each elementary step of the mechanism.