Jawaharlal Nehru Technological University Hyderabad B.Tech I Year ENGINEERING CHEMISTRY Previous Question Paper (October/November - 2020 - R15)

A methanol-oxygen fuel cell (DMFC) is a type of proton-exchange fuel cell where methanol is used as the fuel. Its advantages include:

• High Energy Density: Methanol is a liquid at room temperature, making it easier to store and transport compared to gaseous hydrogen.
• Ease of Handling: It does not require complex high-pressure storage tanks, reducing safety risks.
• Continuous Operation: It provides a steady supply of power as long as fuel and oxidant are supplied.
• Environmental Friendliness: The primary byproducts are carbon dioxide and water, making it a cleaner energy source than fossil fuels.

Applications include:

• Powering portable electronic devices like laptops and mobile phones.
• Use in military field equipment where portability and long-duration power are required.
• Applications in small-scale remote power generation and backup power systems.

The pH of a solution is determined using a glass electrode by measuring the potential difference between a glass electrode (indicator electrode) and a reference electrode (typically a saturated calomel electrode, SCE). The potential of the glass electrode depends on the hydrogen ion concentration of the test solution.

The cell assembly is represented as: Ag/AgCl | 0.1M HCl | Glass membrane | Test solution || SCE

The potential of the glass electrode is given by the Nernst equation:

The steps for determination are:

1. Calibration: The pH meter is calibrated using standard buffer solutions of known pH (e.g., pH 4.0, 7.0, and 9.2).
2. Immersion: The glass electrode and the reference electrode are cleaned with distilled water and immersed into the test solution.
3. Measurement: The potential difference (EMF) is measured by the potentiometer. Since the potential of the reference electrode is constant, the change in EMF is directly proportional to the pH of the solution.
4. Calculation: The pH meter converts the measured EMF into a direct pH reading based on the calibration curve.