a) What causes the permanent hardness of water? Mention one method to remove permanent hardness.
(b)What do you understand by electron-rich hydrides ? Give an example.
©Complete the following chemical reaction equation :
(b)Electron-rich hydrides have excess of electrons which are present as lone pairs. Elements of group 15-17 form such compound. (N${{H}{3}} has one lone pair, {{H}{2}}$0 has two and HF has three lone pairs of electrons). They will behave as Lewis bases, i.e., electron-donors.
