The synthesis of barium sulfate was performed by dissolving 2.00 g of sodium sulfate in water and adding the solution to another solution prepared by dissolving 2.50 g of barium chloride in water. The
precipitate consisting of barium sulfate was filtered, washed, dried and weighed. The mass of the
precipitate was found to be 2.56 g.
Na SO.(aq) + BaCl2(aq) → BaSO.(s) + 2 NaCl(aq)
a) Calculate the moles of each reactant.

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explanation:

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.