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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Answer:
C
Explanation:
Exothermic means that heat is released from the reaction
You must remember that oxidation number of hydrogen in acids is always +1, oxidation number of oxygen in oxides & acids is always -2... metals has always oxidation number on plus!
group NO3 comes from HNO3...and oxidation number of whole acid group is always on minus and equal to the amount of hydrogen atoms in this acid... so oxidation number of NO3 = -1
we have 2 NO3 groups so 2*(-1) = -2 and that is the reason why oxidation number of Fe in this formula must be +2... because sum of all elements always gives 0!
Now we could count of oxidation number for nitrogen... we write HNO3 and start counting from right to left:
3*(-2) from oxygens + 1 from hydrogen = -5
so nitrogen must have +5 oxidation number... because sum all in formula must be 0.
I’ve been having problems too honestly lol
