Chemistry Class 12 NCERT Solutions: Chapter 7 The p Block Elements Part 4

Download PDF of This Page (Size: 162K)

Q: 25. Explain why inspite of nearly the same electronegativity, oxygen forms hydrogen bonding while chlorine does not.

Answer

Both chlorine and oxygen have almost the same electronegativity values, but chlorine rarely forms hydrogen bonding. This is because in comparison to chlorine, oxygen has a smaller size and as a result, a higher electron density per unit volume.

Q: 26. Write two uses of .

Answer:

Uses of :

(i) It is used for purifying water.

(ii) It is used as a bleaching agent

Q: 27. Why are halogens coloured?

Answer

Almost all halogens are coloured. This is because halogens absorb radiations in the visible region. This results in the excitation of valence electrons to a higher energy region. Since the amount of energy required for excitation differs for each halogen, each halogen displays a different colour.

Q: 28. Write the reactions of and with water.

Answer

(i)

(ii)

Q: 29. How can you prepare from and HCl from ? Write reactions only.

Answer:

(i) can be prepared from by Deacon’s process

(ii) can be prepared from on treating it with water

Q: 30. What inspired . Bartlett for carrying out reaction between and ?

Answer:

Neil Bartlett initially carried out a reaction between oxygen and . This resulted in the formation of a red compound, .

Later, he realized that the first ionization energy of oxygen and is almost the same. Thus, he tried to prepare a compound with and . He was successful and a red-coloured compound, was formed.

Q: 31. What are the oxidation states of phosphorus in the following:

(i) (ii) (iii)

(iv) (v) ?

Answer:

Let the oxidation state of be

(i)

(ii)

(iii)

(iv)

(v)

Q: 32. Write balanced equations for the following:

(i) is heated with sulphuric acid in the presence of

(ii) Chlorine gas is passed into a solution of in water.

Answer:

(i)

(ii)