1) The overall balanced photosynthesis reaction:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Plants convert solar energy into the chemical energy of sugars (food).
2) Chemical reaction of cellular respiration:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.
Organic carbon (glucose) is transformed into inorganic carbon (carbon dioxide) that goes into atmosphere.
3) Gasoline combustion:
C₈H₁₈ + 25/2O₂ → 8CO₂ + 9H₂O.
Gasoline is a mixture of many different hydrocarbons: alkanes (paraffins), cycloalkanes and alkenes (olefins).
Gasoline is being burn.
4) Balanced chemical reaction of forming rust: 4Fe + 3O₂ → 2Fe₂O₃.
Forming rust usually last for few months and iron changing in another substance with different properties.
5) An electrochemical cell (voltaic or galvanic cell) is generating electrical energy from chemical reactions.
In galvanic cell, specie (for example zinc and zinc cations) from one half-cell, lose electrons (oxidation) and species from the other half-cell (for example copper and copper cations) gain electrons (reduction).
Oxidation on the zinc anode: Zn(s) → Zn²⁺(aq) + 2e⁻.
Reduction on the copper cathode: Cu²⁺(aq) + 2e⁻ → Cu(s).
Copper is forming from the solution, that is chemical change.
6) Balanced chemical reaction: CaO + H₂O → Ca(OH)₂.
Making limewater (diluted solution of calcium hydroxide).
7) Neutralization is reaction in which an acid and a base react quantitatively with each other. In this reaction, there are no acids and bases, only salts.
Balanced chemical reaction of vinegar and antacid:
2CH₃COOH(aq) + Mg(OH)₂(aq) → (CH₃COO)₂Mg(s) + 2H₂O(l).
Precipation is formed.
8) Balanced chemical reaction of magnesium and hydrochloric acid:
MgO + 2HCl → MgCl₂ + H₂O(g).
Acid dissolves metal oxides.
9) Chemical reaction of silver in air:
4Ag + 2H₂S + O₂ → 2Ag₂S (tarnish) + 2H₂O.
Silver change color in the air.
10) Forming of patina: 2CuO + CO₂ + H₂O → Cu₂CO₃(OH)₂.
Brass (copper) change color to green.
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