Why `He_2` is not formed?

Why a precipitate of Mg(OH)_2 is not formed when aqueous ammonia, NH_4 OH is added to a solution of MgCl_2 ?

Echo is not formed in a small room Why ?

Why is food chain formed in a nature?

Why are the offspring formed by asexual reprodution referred to as clones?

What is the use of diborane ? Why BH_(3) exists in the form of diborane ?

Why does boron form stable electron deficient compounds ?

In the preparation of H_(2)SO_(4) by contact process, why is SO_(3) not absorbed directly in water to form H_(2)SO_(4) ?

Why hard water does not form lather with soap ? What advantage has soap over detergents ?

Ahmad took a magnesium ribbon and burned it on a flame. The white powder formed was taken in a test tube and water was added to it. He then tested the solution formed with red and blue litmus paper. What change was seen ? Why ?