Question

hydrogen peroxide can be used to disinfect and clean surfaces around the home. it breaks down over time into oxygen gas and water. consider the following reaction: some amount of hydrogen peroxide (h₂o₂) breaks down to produce 2 molecules of oxygen (o₂) and 4 molecules of water (h₂o). complete the table below. chemical element | number of atoms in the reaction h | o | during this reaction, how many molecules of hydrogen peroxide (h₂o₂) react?

Explanation:

Part 1: Completing the table for number of atoms

For Hydrogen (H):

Step 1: Calculate H from water

Each water molecule ($\ce{H2O}$) has 2 H atoms, and there are 4 water molecules. So H from water: $4 \times 2 = 8$.
Hydrogen peroxide is the only other source, but let's check conservation. Wait, actually, in the products, water has H. So total H atoms: from 4 $\ce{H2O}$: $4\times2 = 8$.

Step 2: Confirm (no other H sources), so total H atoms = 8.

For Oxygen (O):

Step 1: Calculate O from oxygen gas

Each $\ce{O2}$ molecule has 2 O atoms, 2 molecules: $2\times2 = 4$.

Step 2: Calculate O from water

Each $\ce{H2O}$ has 1 O atom, 4 molecules: $4\times1 = 4$.

Step 3: Total O atoms: $4 + 4 = 8$.

Part 2: Number of $\ce{H2O2}$ molecules reacting

Step 1: Use conservation of H

Each $\ce{H2O2}$ has 2 H atoms. Let $n$ be the number of $\ce{H2O2}$ molecules. Total H from reactants: $2n$. From products (water), total H is 8 (from part 1). So $2n = 8$ → $n = 4$? Wait, no, wait. Wait, products: 4 $\ce{H2O}$ (each has 2 H) → 8 H. Reactants: $\ce{H2O2}$ has 2 H per molecule. So $2n = 8$ → $n = 4$? Wait, but let's check O.

Step 2: Use conservation of O

Each $\ce{H2O2}$ has 2 O atoms. So O from reactants: $2n$. From products: 2 $\ce{O2}$ (4 O) + 4 $\ce{H2O}$ (4 O) → 8 O. So $2n = 8$ → $n = 4$. Wait, but let's check the reaction equation. Wait, the products are 2 $\ce{O2}$ and 4 $\ce{H2O}$. Let's write the reaction:

$\ce{n H2O2 -> 2 O2 + 4 H2O}$

Balance H: left: 2n H; right: 4×2 = 8 H → 2n = 8 → n=4.

Balance O: left: 2n O; right: 2×2 + 4×1 = 8 O → 2n=8 → n=4. So n=4.

Answer:

s:

Table:

• H: 8
• O: 8

Number of $\ce{H2O2}$ molecules: 4