State the chemical formula for each compound.

• a) Nitrogen gas: Nitrogen exists as a diatomic molecule. $$\boxed{\text{N}_2}$$
• b) Carbon (IV) oxide: Carbon with an oxidation state of +4, bonded to oxygen. This is commonly known as carbon dioxide. $$\boxed{\text{CO}_2}$$
• c) Ammonia: A common inorganic compound of nitrogen and hydrogen. $$\boxed{\text{NH}_3}$$

• i) $\text{CH}_3\text{C}(=\text{O})\text{OCH}_2\text{CH}_3$ This is an ester. The acid part is derived from ethanoic acid (2 carbons), and the alcohol part is derived from ethanol (2 carbons). $$\boxed{\text{Ethyl ethanoate}}$$
• ii) $\text{CH}_3\text{CH}_2\text{C}(=\text{O})\text{OCH}_2\text{CH}_2\text{CH}_3$ This is an ester. The acid part is derived from propanoic acid (3 carbons), and the alcohol part is derived from propanol (3 carbons). $$\boxed{\text{Propyl propanoate}}$$
• iii) $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}$ This is a primary alcohol with a 4-carbon chain and the hydroxyl group on the first carbon. $$\boxed{\text{Butan-1-ol}}$$

The formula $\text{C}_5\text{H}_{10}$ indicates that the compounds are either alkenes (containing one double bond) or cycloalkanes.

• Alkenes:

  1. Pent-1-ene $$\text{CH}_2=\text{CH}-\text{CH}_2-\text{CH}_2-\text{CH}_3$$
  2. Pent-2-ene (cis and trans isomers exist, but only the structural isomer is shown) $$\text{CH}_3-\text{CH}=\text{CH}-\text{CH}_2-\text{CH}_3$$
  3. 2-Methylbut-1-ene $$\text{CH}_2=\text{C}(\text{CH}_3)-\text{CH}_2-\text{CH}_3$$
  4. 3-Methylbut-1-ene $$\text{CH}_2=\text{CH}-\text{CH}(\text{CH}_3)-\text{CH}_3$$
  5. 2-Methylbut-2-ene $$\text{CH}_3-\text{C}(\text{CH}_3)=\text{CH}-\text{CH}_3$$

• Cycloalkanes: 6. Cyclopentane $\begin{smallmatrix} \text{CH}_2-\text{CH}_2 \\ | \quad \quad | \\ \text{CH}_2 \quad \text{CH}_2 \\ \quad \backslash / \\ \quad \text{CH}_2 \end{smallmatrix}$ 7. Methylcyclobutane $\begin{smallmatrix} \text{CH}(\text{CH}_3)-\text{CH}_2 \\ | \quad \quad \quad | \\ \text{CH}_2 \quad \quad \text{CH}_2 \end{smallmatrix}$ 8. 1,1-Dimethylcyclopropane $\begin{smallmatrix} \quad \text{CH}_2 \\ \quad / \quad \backslash \\ \text{C}(\text{CH}_3)_2-\text{CH}_2 \end{smallmatrix}$ 9. 1,2-Dimethylcyclopropane (cis and trans isomers exist, but only the structural isomer is shown) $\begin{smallmatrix} \quad \text{CH}(\text{CH}_3) \\ \quad / \quad \quad \backslash \\ \text{CH}(\text{CH}_3)-\text{CH}_2 \end{smallmatrix}$ 10. Ethylcyclopropane $\begin{smallmatrix} \quad \text{CH}_2 \\ \quad / \quad \backslash \\ \text{CH}(\text{CH}_2\text{CH}_3)-\text{CH}_2 \end{smallmatrix}$