A chemical reaction occurs when substances change. Photosynthesis is the process by which plants produce food.
1) A chemical reaction is a process by which substances can be changed into other substances. Hence, in a chemical reaction, new substances are formed.
2) Photosynthesis is the process by which plants produce food using carbon dioxide and water in the process of sunlight and chlorophyll. Glucose is produced during photosynthesis and the energy produced and stored as starch.
3) Valence electrons show the kind of bond that an atom can form. Reaction between two atoms that have many valence electrons is most likely covalent. An ionic bond is formed between an atom that has few valence electrons and an atom that has many valence electrons.
4) A carbohydrate is a compound that comprises of hydrogen and oxygen in a ratio of 2:1. The compound that is a carbohydrate is C3H6O3.
5) Rocks contain iron. Iron oxides form when cyanobacteria produce oxygen via photosynthesis.
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A food web shows all of the possible energy pathways through an ecosystem.
Answer:



Explanation:
(a)
The balanced chemical equation for the reaction of methane with oxygen gas to form carbon dioxide and water is shown below as;

(b)
The balanced chemical equation for the reaction of butane with oxygen gas to form carbon dioxide and water is shown below as;

(c)
The balanced chemical equation for the reaction of solution of sulfuric acid reacts with aqueous potassium hydroxide to produce potassium sulfate and water is shown below as;

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Balanced chemical reaction:
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l).
Calcium carbonate (CaCO₃) dissolves in hydrochloric acid and gas carbon(IV) oxide is formed.
Calcium carbonate is inorganic salt insoluble in water, but soluble in acidic solutions.