Define "enantiomer" and "diastereomer"

Enantiomers are the non-superimposable mirror images of each other.

Diastereomers are the stereisomers that are not a reflection or mirror images of each other.  

Explanation:

Stereoisomers are the chemical molecules having the same molecular formula and bond connectivity but different arrangement of atoms in space.

Stereoisomers are of two types: Enantiomers and Diastereomers

Enantiomers are the non-superimposable mirror images of each other. Enantiomers are also called optical isomers.

Diastereomers are the stereisomers that are not a reflection or mirror images of each other. Diastereomers include E-Z isomers, cis–trans isomers, meso compounds, non-enantiomeric optical isomers.

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation:

dynamic equilibrium is the answer.