Phosphoric acid can be prepared by reaction of sulfuric acid with “phosphate rock”
according to the equation:
Ca3(PO4)2 + 3H2SO4  3CaSO4 + 2H3PO4
What is the molar mass of Ca3(PO4)2?

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.