A sample of neon effuses from a container in 38 s. The same amount of an unknown noble gas requires 77.5 s. What is the unknown gas?

Krypton.

Explanation:

By Graham's Law:

Rate 1 / Rate 2 = sqrt M2 / sqrt M1

Molecular Mass for Neon  is 20.18

so we have:

38 / 77.5  =  sqrt 20.18 / sqrt x    where x is the unkown gas.

sqrt x = 9.162

x = 83.94.

This gas is Krypton.

dynamic equilibrium is the answer.

  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-