Energy is required to melt a solid because the cohesive bonds between the molecules in the solid must be broken apart so that the molecules can move around at comparable kinetic energies
Boric acid, H3BO3, in aqueous solution would only give out one H+ ion. As it is also produce OH ion and by hydrolysis it produces one proton. <span>All the boron compounds (BX3) are having only 6 valence electrons in it and should follow the octet rule by taking another electron.</span>
B(OH)3 + 2 H2O → B(OH)4− + H3O
The boiling point of a liquid can be raised by adding pressure. Like wise, if you lower the pressure the boiling point goes down. This can be explained by the fact that boiling occurse when the vapor pressure equals the outside pressure so when the outside pressure rises the vapor pressure required for boiling also rises. Vapor pressure is proportional to temperature and therefore temperature needs to increase to make the vapor pressure increase.
I hope this helps. Let me know in the comments if anything is unclear or if you want me to explain anything further.