The electron affinity of second member in group 15, 16 ,and 17 is higher than that of first member of the same group because of 

• very small size of of the first element  ,  2p -elements ( whose atoms consist of  s and p orbitals only )

          The very small size of the first element in these groups results into overcrowding of electrons in a small volume .The mutual                 repulsion of electrons , therefore , resists probability of admitting  additional  electrons  . thereby reducing electron affinity. 

• In case of second element of the same group  the atoms are large due to presence of  s, p, and also d - orbitals , and  tendency to admit additional electron in its atom increases .Thus the electron affinity becomes more negative ,which means a greater electron affinity. 

Yes , the chapter 2 / solutions is quite important from  cbse class 12 examination point of view , and hence must not be ignored . Short answer type -1 questions (1 mark ) and Short  answer type -2 questions ( 2 -3 marks ) along with the numericals  usually appear in the chemistry question paper.

The topics or different units should be well understood  before attempting the given intext questions  as well as the exercises . The following must be learnt well ,     

1. molarity , molality  and mole fraction .

2.   Henry's law and   its expression as a fomula , applications of  Henry's law .

3 Raoult's law  and related formulae  for liquid -liquid solutions , and  solutions containing nonvolatile solutes.

4.  Colligative properties , ideal and nonideal solutions  &  deviations of nonideal solution wit respect to ideal solution .

5.  Osmosis and osmotic pressure .

6. Application of formulae  ( viz  {tex}\Delta{/tex}.T_b  ,{tex}\Delta{/tex}T_f ,{tex}\pi{/tex} ( Osmotic pressure )  and  i (vant Hoff's factor ) and also reverse osmosis.

Further , it is a regular and  constant practice or revision   which  makes us perfect in any topic. So,  work out all the questions  patiently . Wish you all the best . 

d-block elements are most  suitable  to form a coordination compound / complex  because of

the presence of  vacant or unpaired  electrons in d - block or  transition elements  as central atom in a coordination compound results into its coordination  with  ligands which are electron  donors.  

Inverted or invert sugar syrup is a mixture of glucose and fructose; it is obtained by splitting the disaccharidesucrose into these two components. Compared with its precursor, sucrose,inverted sugar is alluringly sweet and its products tend to retain moisture and are less prone to crystallization.

 The Hoopes process is a metallurgical process, used to obtain the aluminium metal of very high purity. It is a method used to obtain aluminium of very high purity. The metal obtained in the Hall-Heroult process is about 99% pure, and for most purposes it is taken as pure metal. However, further purification of aluminium can be carried out by the Hoopes process. This is an electrolytic process.

It is a method used to obtain aluminium of very high purity. The metal obtained in the Hall-Heroult process is about 99% pure, and for most purposes it is taken as pure metal. However, further purification of aluminium can be carried out by the Hoopes process. This is an electrolytic process.

A free neutron is unstable , decaying to proton , electron and antineutino with a mean life of  ~ 15 minutes (  881.5  _-+ 1.5 s )

This radioactive decay ,is known as{tex}\beta{/tex} - decay.

The strong and weak electrolytes are separately defined as ,

Strong  electrolytes - 

Strong electrolyte is a solute that completely ( or almost completely ) , ionises (( ie. ~100% ionisation )  in its solution , and are good conductors of electric current  .

Weak electrolytes -

A weak electrolyte is a substance that does not completely dissociate  ,  or partially ionise  ( ~ 1 - 10% )  in its aqueous solution

A few examples of nonideal solutions showing  positive and negative deviation from Rault's law are ,

The treatment of alkyl halide with aqueous KOH solution leads to the formation of  alcohols  because -

Aqueous KOH ionises to form hydroxyl ions ( OH^- ) . Since OH^- ion is a strong nucleophile  it brings about substitution reaction  with alkyl halides forming alcohols.

                     KOH (aq)   -------------->   K⁺ (aq)      +    OH^- (aq)

                       RCl   +   OH ^- _(aq) ------------>   R-OH      +    Cl^- _(aq)

but with alcoholic KOH solution ,an alkene is formed .

This is  due to formation of an  alkoxide ion (RO^- ) . The alkoxide ions are much stronger bases  than OH^- ions  and eliminates a molecule of HCl   from alkyl halide to form alkenes 

                 C₂ H₅ Cl   +   KOH (alcoholic)   ------------>    CH₂  =  CH₂   +   KCl      +   H₂O

The molecularity of a reaction is defined as the total number of reactant molecules or atoms taking part in a chemical reaction .

or, in terms of collision theory ,

It is the number of species which undergo collision to result into a chemical reaction 

The reaction is termed as unimolecular , bimolecular or trimolecular depending upon the reacting particles ( ie. atoms , molecules or ions ) as 1,2 or 3 etc. in the rate determining step.

Examples :

The following images depict  a few examples  &  also  certain points to consider  while  inferring molecularity of a reaction .

1.

2.   (Important)

The Molecularity of a reaction is defined as the total number of reactant molecules or atoms taking part in the Chemical Reaction. The reaction are termed as unimolecular , bimolecular or termolecular etc.