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A chemical equation is shown:

[tex]\( C_2H_4 + O_2 \rightarrow CO_2 + H_2O \)[/tex]

According to the law of conservation of mass, how many atoms of oxygen exist in the products of this reaction?

A. 2
B. 4
C. 6



Answer :

To solve this problem, let's balance the given chemical equation and tally the number of oxygen atoms present in the products:

1. Chemical Equation Given:
[tex]\[ C_2H_4 + O_2 \rightarrow CO_2 + H_2O \][/tex]

2. Balancing the Chemical Equation:
To balance the equation, we need the same number of each type of atom on both sides of the equation. Let's start by balancing one element at a time.

Balancing Carbon (C):
- There are 2 carbon atoms in [tex]\(C_2H_4\)[/tex].
- Thus, we need 2 molecules of [tex]\(CO_2\)[/tex].
[tex]\[ C_2H_4 + O_2 \rightarrow 2CO_2 + H_2O \][/tex]

Balancing Hydrogen (H):
- There are 4 hydrogen atoms in [tex]\(C_2H_4\)[/tex].
- Thus, we need 2 molecules of [tex]\(H_2O\)[/tex] (each containing 2 hydrogen atoms).
[tex]\[ C_2H_4 + O_2 \rightarrow 2CO_2 + 2H_2O \][/tex]

Balancing Oxygen (O):
- On the right side (products), we have:
- 2 [tex]\(CO_2\)[/tex] molecules, and each has 2 oxygen atoms, contributing [tex]\(2 \times 2 = 4\)[/tex] oxygen atoms.
- 2 [tex]\(H_2O\)[/tex] molecules, and each has 1 oxygen atom, contributing [tex]\(2 \times 1 = 2\)[/tex] oxygen atoms.
- Therefore, the total number of oxygen atoms is [tex]\(4 + 2 = 6\)[/tex].
- On the left side (reactants), we need 6 oxygen atoms. Each [tex]\(O_2\)[/tex] molecule has 2 oxygen atoms.
- Therefore, we need [tex]\(3 \times O_2\)[/tex] molecules to make 6 oxygen atoms.
[tex]\[ C_2H_4 + 3O_2 \rightarrow 2CO_2 + 2H_2O \][/tex]

3. Identify Oxygen Atoms in Products:
- From the balanced chemical equation:
[tex]\[ C_2H_4 + 3O_2 \rightarrow 2CO_2 + 2H_2O \][/tex]
- We have:
- [tex]\(2CO_2\)[/tex] contributing 4 oxygen atoms.
- [tex]\(2H_2O\)[/tex] contributing 2 oxygen atoms.
- Therefore, the total number of oxygen atoms in the products is:
[tex]\[ 4 + 2 = 6 \][/tex]

Hence, the number of oxygen atoms present in the products of this reaction is [tex]\(6\)[/tex]. The correct answer is [tex]\(6\)[/tex].

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