The following is a partial chemical equation: ? → CO2 + 2H20
What can you infer about the reactants in this reaction?
A. The reactants include 2 carbon dioxide molecules and 1 water
molecule.
B. The reactants include 1 carbon dioxide molecule and 2 water
molecules.
O C. The reactants include 1 carbon atom, 2 oxygen atoms, and 2 water
molecules.
D. The reactants include 1 carbon atom, 4 oxygen atoms, and 4
hydrogen atoms.

Option D

Explanation:

A chemical reaction, in general, has two sides. A reactant side, and a a product side.

The products of a chemical reaction doesn't necessarily have the compounds of the reactants, in fact, it usually begins with different compounds to form another compound. This is actually what makes sense of a chemical reaction.

But, a chemical reaction needs to be balanced, which means that no matter what compound or element we have in the reactants, we should have the same number of atoms and element on each side of the reaction.

Now, according to the given chemical reaction, the products of this reaction are CO₂ and H₂O. You can also see that the water molecule has a number 2, behind the compound. This number represents, chemically speaking, number of moles of the compound, but it also tell us another information and its the fact that this number multiply the number of atoms of the compound. So, if we have 2H₂O, then we actually have 2 atoms of oxygen, and 4 atoms of hydrogen.

In the case of CO₂, we only have 1 atom of carbon and 2 atoms of oxygen. The information we can get from this, and according to the above explanation, we should have in the reactants, one or more compounds that have in its inner structure, Carbon, oxigen and hydrogen; it doesn't necessarily mean that it should be one compound at once, it could be 2 or more compounds, but these elements have to be in there.

How many atoms of each element? We said it before, a chemical reaction needs to be balanced, so if we have in the products, 2 atoms of Carbon, 4 atoms of hydrogen and 4 atoms of oxygen (2 from the CO₂ and 2 from the water), then in the reactants, we need to have 4 atoms of hydrogen and oxygen, and 1 atom of Carbon at least.

The correct option should be D.

Hope this helps

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