5.Are pure solids included in equilibrium expressions? Explain your answer.

Answer /Explanation:

Corresponding Equilibrium Expression: Pure solids or liquids are excluded from the equilibrium expression because their effective concentrations stay constant throughout the reaction. The concentration of a pure liquid or solid equals its density divided by its molar mass.

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.