9. Which of the following equations represent redox reactions? For each redox reaction,
determine which atom is oxidized and which
is reduced, and identify the oxidizing agent
and the reducing agent.
a. MgO(s) + H2CO3(aq) →

MgCO3(s) + H2O(l)
b. 2KNO3(s) → 2KNO2(s) + O2(g)
c. H2(g) + CuO(s) → Cu(s) + H2O(l)
d. NaOH(aq) + HCl(aq) →NaCl(aq) + H2O(l)
e. H2(g) + Cl2(g) → 2HCl(g)
f. SO3(g) + H2O(l) → H2SO4(aq)

the answer would be c

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.