Question

which of the following sets of coefficients will balance the reaction? _h₂o₂→_h₂o+_o₂
a) 2, 2, 1
b) 1, 2, 2
c) 4, 4, 1
d) 3, 2, 1
the subscript in a chemical formula represents the number of what?
a) molecules of reactants
b) number of compounds
c) atoms of an element
d) charge of the ions

Explanation:

Step1: Balance the chemical equation

For the reaction \( \text{H}_2\text{O}_2
ightarrow\text{H}_2\text{O}+\text{O}_2 \), we check each option.

• Option A: \( 2\text{H}_2\text{O}_2

ightarrow2\text{H}_2\text{O}+\text{O}_2 \)

• Hydrogen atoms: Left side \( 2\times2 = 4 \), right side \( 2\times2 = 4 \)
• Oxygen atoms: Left side \( 2\times2 = 4 \), right side \( (2\times1)+2 = 4 \)
• Option B: \( 1\text{H}_2\text{O}_2

ightarrow2\text{H}_2\text{O}+2\text{O}_2 \)

• Hydrogen atoms: Left side \( 2 \), right side \( 2\times2 = 4 \) (not balanced)
• Option C: \( 4\text{H}_2\text{O}_2

ightarrow4\text{H}_2\text{O}+1\text{O}_2 \)

• Oxygen atoms: Left side \( 4\times2 = 8 \), right side \( (4\times1)+2 = 6 \) (not balanced)
• Option D: \( 3\text{H}_2\text{O}_2

ightarrow2\text{H}_2\text{O}+1\text{O}_2 \)

• Hydrogen atoms: Left side \( 3\times2 = 6 \), right side \( 2\times2 = 4 \) (not balanced)

Step2: Determine the meaning of subscript

In a chemical formula like \( \text{H}_2\text{O} \), the subscript \( 2 \) in \( \text{H}_2 \) represents the number of hydrogen atoms.

• Option A: Molecules of reactants are represented by coefficients (e.g., \( 2\text{H}_2\text{O}_2 \)), not subscripts.
• Option B: Number of compounds is not indicated by subscripts.
• Option C: Correct as subscripts show the number of atoms of an element.
• Option D: Charge of ions is shown with superscripts (e.g., \( \text{Na}^+ \)), not subscripts.

Answer:

For the balancing coefficients question: A. \( 2,2,1 \)
For the subscript meaning question: C. Atoms of an element