1.
a. Ar(Na) = 23
b. Ar(Br) = 80
c. Ar(Pb) = 207
2.
a. Mr(Al2O3) = 2Ar(Al) + 3Ar(O) = 2 * 27 + 3 * 16 = 102
b. Mr(KMnO4) = Ar(K) + Ar(Mn) + 4Ar(O) = 39 + 55 + 4 * 16 = 158
c. Mr(CH3COOH) = 4Ar(H) + 2Ar(C) + 2Ar(O) = 4 * 1 + 2 * 12 + 2 * 16 = 60
d. Mr(C6H12O6) = 6Ar(C) + 12Ar(H) + 6Ar(O) = 6 * 12 + 12 * 1 + 6 * 16 = 180
3.
a. 4Al + 3O2 = 2Al2O3
b. H2O + SO3 = H2SO4
c. CaO + CO2 = CaCO3