Question

1. first, select the model of a molecule composed of two carbon atoms and four hydrogen atoms.

then, select the chemical formula for the substance composed of these molecules.

Explanation:

Part 1: Select the molecule model (Ethylene, Methane, Ethane)

1. Methane: Has 1 carbon and 4 hydrogens ($CH_4$), so the middle model (1 C, 4 H) is methane.
2. Ethane: Has 2 carbons and 6 hydrogens ($C_2H_6$), so the right model (2 C, 6 H) is ethane.
3. Ethylene (Ethene): Has 2 carbons and 4 hydrogens ($C_2H_4$), with a double bond. The left model (2 C, 4 H, double bond) is ethylene.

The molecule with 2 C and 4 H is ethylene (ethene).

1. Step 1: Ethylene’s formula: Ethylene (ethene) has the formula $C_2H_4$.
2. Step 2: Multiply by 10: For 10 molecules, the formula is $10 \times C_2H_4 = C_{20}H_{40}$? Wait, no—wait, the question says "the substance composed of 10 such molecules" (assuming "such" refers to ethylene). Wait, maybe a typo? Wait, original problem: "the chemical formula for the substance composed of 10 such molecules" (ethylene, $C_2H_4$). So 10 molecules of $C_2H_4$ would be $10C_2H_4$, but if it’s a single formula (like a polymer? No, 10 molecules of ethylene). Wait, maybe the options? Wait, the given options: $C_2H_4$, $CH_4$, $C_{10}H_20$? Wait, no—wait, the user’s image shows "C₂H₄", "CH₄", "C₁₀H₂₀"? Wait, maybe the question is about the formula for ethylene (1 molecule) or 10 molecules. Wait, ethylene’s formula is $C_2H_4$. If 10 molecules, it’s $10C_2H_4$, but maybe the question is misphrased. Alternatively, maybe it’s a polymer, but no—10 molecules of ethylene would be $10C_2H_4$. But if the options include $C_{10}H_{20}$, that’s wrong. Wait, maybe the question is "the chemical formula for the substance (ethylene) composed of 10 such molecules"—no, ethylene is $C_2H_4$ per molecule. Wait, maybe the answer is $C_2H_4$ (for one molecule) or $10C_2H_4$. But given the options, $C_2H_4$ is ethylene’s formula.

Step-by-Step:

Step 1: Identify Ethylene’s Formula

Ethylene (ethene) has 2 C and 4 H per molecule: $C_2H_4$.

Step 2: Formula for 10 Molecules

For 10 molecules, the formula is $10 \times C_2H_4 = 10C_2H_4$. But if the question means the empirical formula or molecular formula of the substance (assuming 10 molecules as a unit), but typically, molecular formula for ethylene is $C_2H_4$. If the options include $C_2H_4$, that’s the answer.

Answer:

Left model (labeled "ethylene" or "ethene")

Part 2: Chemical formula for 10 ethylene molecules