Balanced chemical reaction: 4Al + 3O₂→ 2Al₂O₃.
a) Oxidation half-reaction: Al⁰ → Al⁺³ + 3e⁻ /×4; 4Al⁰ → 4Al⁺³ + 12e⁻.
b) Reduction half-reaction: 4e⁻ + O₂ → 2O⁻² /×3; 12e⁻ + 3O₂ → 6O⁻².
Oxidation is increase of oxidation number, aluminium change oxidation number from zero to +3 and reduction is decrease of oxidation number, oxygen from 0 to -2.
The number of atoms in 12 grams of the isotope carbon 12.
Answer:
50g of CaCO3=1. 5∗(6. 022∗1023)=9. 035∗1023 oxygen atoms