Question

apply: counting atoms in chemical equations
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how many hydrogen atoms are on the left side of the following chemical equation?
$2\\,\mathrm{c}_2\mathrm{h}_6 + 7\\,\mathrm{o}_2 \
ightarrow 4\\,\mathrm{co}_2 + 6\\,\mathrm{h}_2\mathrm{o}$
hydrogen atoms
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Explanation:

Step1: Identify the compound with H on the left.

The left side of the equation is \(2 \ce{C_2H_6} + 7 \ce{O_2}\). The compound with hydrogen is \(\ce{C_2H_6}\), and its coefficient is 2.

Step2: Find H atoms in one \(\ce{C_2H_6}\).

In one \(\ce{C_2H_6}\) molecule, there are 6 hydrogen atoms (from the subscript 6 on H).

Step3: Calculate total H atoms.

Multiply the number of \(\ce{C_2H_6}\) molecules (2) by the number of H atoms per molecule (6): \(2\times6 = 12\).

Answer:

12