Ncert Solutions Chemistry Class 12th

4.14 Factors affecting rate of reaction-

1) Temperature (increasing temperature increases rate of reaction)

2) Concentration or pressure of reactants. (Increasing concentration or pressure increases rate of reaction)

3) Presence or absence of a (Adding catalyst mostly increases the rate of reaction)

4) The surface area of solid (If reaction is processing over solid reactant then increasing its surface area increases rate of reaction)

5) Nature of reactants

5.5

Ester hydrolysis is represented as:

Ester + Water → Acid + Alcohol

In this reaction the acid produced which is a product also acts as a catalyst and makes the reaction faster.

Such substances that act as catalysts in the same reaction in which they are obtained as products are known as Autocatalysts.

So, ester hydrolysis is slow in the beginning and becomes faster after some time as more acid is produced on the product side.

4.13 Rate of given chemical reaction will be represented as

-d [pCH₃OCH₃] / dt

Hence units of rate is bar min^-1

To find units of K, K = rate/ [pCH₃OCH₃]^3/2

The unit of k = bar ^-1/2min^-1.

Units of Rate- bar min^-1. and Units of Rate constant K : bar ^-1/2min ^-1

5.4

It is important to remove CO (Carbon Monoxide) in the synthesis of ammonia as CO affects the activity of Iron catalyst which is required in Haber's process.

Note: Haber's process is a very important industrial process which is used to produce ammonia.

The colour of the particular complex compound depends on the crystal field splitting energy (CFSE). This CFSE depends on the nature of the ligand attached to the metal atom. In case of [Fe (CN)₆]^4– and [Fe (H2O)₆]²⁺ the colour differs due to differences in CFSE .

CN^- is a strong field ligand so will have high CFSE than H₂O with a low value of CFSE. There is absorption of the energy from the visible region for the d-d transition and corresponding complimentary colour is observed. Thus there is the colour difference.

In case of [Ni (H₂O)₆]²⁺ H₂O is a weak field ligand, so it does not cause the pairing of the unpaired electron of Ni²⁺ ion. Thus there is possibility of the intra d-d transition from the d orbital of lower energy to that of higher energy. Thus the light is absorbed from the visible region and complimentary colour is observed. But in case of [Ni (CN)₄]^2– CN^- is strong field ligand.

Therefore it will cause pairing of the unpaired electrons of Ni²⁺ ion. There are no unpaired electrons present, so there is no d-d transition and hence it is colourless.

5.3

As Adsorption is directly proportional to the available surface area and powdered form of a substance have a greater surface area than the crystalline form of the substance.

So, greater the surface area of the adsorbent more is the adsorption.

Hence, powdered substances are more effective adsorbents than their crystalline forms