Amolecule contains hydrogen bonding if it contains hydrogen covalently bonded to

Fluorine, oxygen, or nitrogen

Explanation:

Hydrogen bridge bond: It is an attraction that exists between a hydrogen atom (positive charge) with a very electronegative small atom, such as fluorine (F), oxygen (O) or nitrogen (N) (FH, OH, NH), which It has a pair of free electrons (negative charge), hence the name "hydrogen bond", which should not be confused with a covalent bond to hydrogen atoms). A hydrogen bridge is actually a dipole-dipole attraction between molecules that contain these three types of polar junctions.

This type of attraction has only a third of the strength of covalent bonds, but it has important effects on the properties of the substances in which they occur, especially in terms of melting and boiling points in crystal structures.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-