Catalysts increase the rate of chemical reactions without being consumed. They work by lowering the activation energy of reactions. Catalytic reactions can be either homogeneous, where reactants and catalysts are in the same phase, or heterogeneous, where they are in different phases. Catalytic reactions are also classified based on their effect - positive catalysts increase reaction rate, negative catalysts decrease it, auto-catalytic reactions use a reaction product as the catalyst, and induced catalytic reactions cause a reaction not otherwise possible.

2. ?
Catalyst is a substance that increases the rate of the reaction at which
a chemical system approaches equilibrium , without being substantially
consumed in the process.
Catalyst affects only the rate of the reaction,i.e.Kinetics.
It changes neither the thermodynamics of the reaction nor the
equilibrium composition.

3. The chemical phenomenon which is influenced by a substance or a set of substances
that remains unchanged at the end of the phenomenon is called catalytic reaction. The
influencing substances are called catalyst.
For example - In Fischer-Tropsch synthesis Ru is used as a catalyst.
(2n+1)H2 + n CO + [Ru] = CnH(2n+2) + H2O + [Ru]
A catalyst increases the forward reaction as well as backward reaction and reduces the
activation energy of a reaction corresponding to the non catalytic reaction of the
reactants.

4. A)According to the phase of reactant, product and
catalyst
Catalytic reaction are of 2 types which are as follow :
 Homogeneous Catalysis:
The reactants and catalyst remain in the same
phase.
For example – In the decomposition of excited NO3* , NO2 is used as
catalyst.
NO3 *(g) + [NO2(g) ] = NO*(g) + O2 (g) + [NO2(g)]

5.  Heterogeneous Catalysis :
The catalytic process in which the reactants
and the catalyst are in different phases is known as heterogeneous
catalysis. Some of the examples of heterogeneous catalysis are given
below.
Oxidation of SO2 to SO3 in the presence of Pt metal or V2O5 as catalyst in
the contact process for the manufacture of sulphuric acid.
SO2 (g) + O2 (g) + Pt (s) = SO3 (g) + Pt (s)
Combination between nitrogen and hydrogen to form ammonia in the
presence of finely divided iron in Haber's process.
N2 (g) + H2 (g) + Fe (s) = NH3 (g) + Fe (s)

6. B). According to the action of catalyst
Catalytic reactions are of 4 types which are as follow :
 Positive Catalytic Reaction
 Negative Catalytic Reaction
 Auto Catalytic Reaction.
 Induced Catalytic Reaction.

7.  Positive Catalytic Reaction:
The typical catalytic reaction on which
the rate of the reaction is increased.
For example – In the production of Oxygen from Potassium chlorate,
Manganese oxide acts as a positive Catalyst.
KClO3 + [MnO2] = KCl + O2 + [MnO2]
 Negative Catalytic Reaction:
The catalytic reaction on which the rate of
the reaction is decreased.
For example – Production of Sodium sulfate from the oxidation of
Sodium sulfide solution is hampered by the presence of ethyl alcohol.
Na2SO3 + O2 + [C2H5OH] = Na2SO4 + [C2H5OH]

8.  Auto Catalytic Reaction:
In some chemical reactions a component from
the products acts as a catalyst i.e. influence the rate of the reaction, such
type reactions are called auto catalytic reaction.
For example – In acidic oxalic acid solution if we add KMnO4 , the color of
KMnO4 disappears slowly but when MnSO4 produced the firstly.
KMnO4 + H2C2O4 + H2SO4 = K2SO4 + MnSO4 + CO2 + H2O

9.  Induced Catalytic Reaction :
When a chemical reactions product
influences the speed of an other reaction which is not possible under
ordinary condition is called as induced catalytic reaction.
For example – the following reactions are induced catalytic Reaction.
Na3AsO3 + O2 = No Reaction
Na2SO3 + O2 = Na2SO4
Na3AsO3 + Na2SO3 + O2 = Na3AsO4 + Na2SO4