13Experimental Protocol and Research Guide: Preparation of Methane (E13)

Institutional Framework and Experimental Task Overview

• Institution and Context: The experiment is conducted within the Institute for Chemistry and Biochemistry – Inorganic Chemistry at the University level, specifically as part of the Internship in General and Inorganic Chemistry (Praktikum Allgemeine und Anorganische Chemie).
• Experiment Designation: Laboratory Work Sheet for Experiment E13, titled "Darstellung von Methan" (Preparation of Methane).
• Primary Objectives:
      - To synthesize methane ($CH_4$) using laboratory methods.
      - To conduct thorough background research on the chemical processes involved.
      - To present findings and practical procedures in a short lecture format (Kurzvortrag) during the introductory course.

Preparatory Research Requirements

• Theoretical Background Recherche: Students are required to consult textbooks for information regarding:
      - The chemical background of the synthesis.
      - Application-oriented facts.
      - Historical context of methane preparation.
      - Specific focus areas: Carbon and its compounds, with a particular emphasis on carbonyl compounds.
• Literature Acquisition:
      - Students must use databases such as SciFinder, the internet, or the university library to find original publications.
      - Although instructions are provided in the work sheet, the original literature serves to deepen the understanding of the underlying chemistry.
      - Original Sources Cite:
          - T.S. Oakwood, M.R: Miller, J. Am. Chem. Soc. 1950, 72, 1849.
          - A. Berthelot, Ann. Chim. Phys. 1866, 4(9), 444.

Investigative Research Questions

Students are tasked with addressing specific scientific questions during their research phase to ensure a comprehensive understanding of the experiment:

• Combustion Processes: Conduct a detailed investigation into the combustion of hydrocarbons.
• Product Analysis: Evaluate whether the combustion of hydrocarbons yields exclusively carbon dioxide ($CO_2$) and water ($H_2O$) or if other products exist.
• Bunsen Burner Mechanics: Explain the physical and chemical processes occurring within a Bunsen burner during operation.
• Chemical Equations: Formulate and verify all relevant reaction equations. Students must be prepared to explain these in detail during their oral presentations.

Safety and Hazard Management

• Chemical Hazards (H- and P-sentences):
      - Students must identify the specific GHS Hazard (H) and Precautionary (P) statements for all chemicals used.
      - The requirement is to internalize this information; students must be able to describe the risks and safe handling procedures in their own words rather than merely reading numerical lists.
• Specific Chemical Risks:
      - Methane ($CH_4$): Classified as highly flammable (hochentzündlich).
      - Sodium Hydroxide ($NaOH$): Classified as strongly corrosive (stark ätzend).
• Safe Handling: Ensuring the test tube is sealed promptly with the bored stopper as instructed to contain the flammable gas.

Experimental Procedure for Synthesis (E13)

• Required Equipment:
      - Stand/support material (Stativ/Stativmaterial).
      - Bunsen burner.
      - Test tube (Reagenzglas).
      - Bored rubber stopper (to be requested from the assistant).
      - Glass tube (pointed/drawn out).
• Required Chemicals:
      - Anhydrous sodium acetate ($CH_3COONa$).
      - Sodium hydroxide pellets ($NaOH$).
• Step-by-Step Instructions:
      1. Measure exactly $3\,g$ of anhydrous sodium acetate.
      2. Mix the sodium acetate with $5$ pellets of $NaOH$ (Sodium Hydroxide) inside a test tube.
      3. Apply heat to the test tube using the Bunsen burner.
      4. Quickly seal the test tube using a stopper that is pierced by a pointed glass tube.
      5. Wait for approximately $30\, ext{seconds}$ to allow the methane gas to displace the air.
      6. Ignite the escaping methane gas at the tip of the glass tube.

Reaction Chemistry and Disposal

• Theoretical Reaction (Decarboxylation of Acetate):
      - While the transcript focuses on procedure, the reaction generally involves the decarboxylation of sodium acetate in the presence of sodium hydroxide (often referred to as soda lime reaction when mixed with lime):
      - $CH_3COONa (s) + NaOH (s) \xrightarrow{\Delta} CH_4 (g) + Na_2CO_3 (s)$
• Waste Management:
      - The residual mixture in the test tube after heating does not contain hazardous chemicals.
      - Procedure: Dilute the residue with water and dispose of it via the laboratory drain (Ausguss).

Documentation and Presentation Standards

• Laboratory Journal (Laborjournal):
      - All observations and experimental conditions must be recorded meticulously.
      - Precise weights (Einwaagen) and other quantitative data must be documented.
      - Photographic documentation of the experimental setup is strongly recommended.
• Presentation (Kurzvortrag):
      - The presentation serves as a preliminary discussion (Vorbesprechung).
      - It is designed as an exercise in explaining complex chemical facts in an understandable manner.
      - Must include a concise explanation of the practical procedure/synthesis.
• Formal Reports (Versuchsvorschriften):
      - For selected experiments, students must submit formal written reports.
      - A template (Muster-Versuchsvorschrift) is provided as a guide for structure and formatting.
      - Further details are provided during the introductory course sessions.