Question

Though heat of combustion of hydrogen is very high, hydrogen is not much used as a fuel because (1) hydrogen is not available as an element (2) preparation of hydrogen gas is costlicr (3) storage and transportation of hydrogen is dangcrous (4) all are correct

Short answer

Option 4: all are correct

Step-by-step solution

Analyze Option 1

Hydrogen is not available as an element in large quantities on Earth. Checking this statement, it’s true that while hydrogen is abundant in compounds like water, it’s not readily available in elemental form.

Analyze Option 2

The preparation of hydrogen gas involves processes like electrolysis or steam reforming, both of which can be costly due to energy requirements and technology involved. This statement is also true.

Analyze Option 3

Hydrogen gas is highly flammable and poses significant risks in storage and transportation. Handling and storing hydrogen require special infrastructure and safety measures. This statement is correct.

Evaluate Option 4

Since options 1, 2, and 3 are all correct statements regarding the challenges of using hydrogen as a fuel, the selection of option 4, which states 'all are correct,' is accurate.

Key concepts

Heat of Combustion

Hydrogen is known for its very high heat of combustion, making it a potent fuel source. When hydrogen combusts with oxygen, it releases a significant amount of energy. This process can be represented by the chemical reaction \[2H_2 + O_2 \rightarrow 2H_2O + \text{energy}\].The major appeal here is the high energy yield combined with the fact that the only byproduct is water, making it theoretically a clean fuel. Despite these advantages, practical issues prevent widespread use of hydrogen fuel.

Hydrogen Availability

Hydrogen is the most abundant element in the universe, but on Earth, it is not readily available in its molecular form, H_2. Most hydrogen is found in compounds like water (H_2O) and hydrocarbons, so it needs to be extracted before use. This extraction process often involves complex and energy-intensive methods such as electrolysis or steam methane reforming.

• Electrolysis: Splitting water into hydrogen and oxygen using electricity.
• Steam Methane Reforming: Reacting natural gas with steam to produce hydrogen.

The challenge of acquiring molecular hydrogen in an efficient and cost-effective manner continues to be a significant barrier for its widespread adoption.

Hydrogen Production Costs

Producing hydrogen can be quite expensive. The primary reason for this is the high energy input required in its production processes. For instance,

• Electrolysis consumes a lot of electricity, making it economically unfeasible in many scenarios.
• Steam reforming requires substantial heat and catalysts, which adds to the cost.

Additionally, to make hydrogen from renewable energy sources, infrastructure and technology need to be developed further. Though there are advancements, the economic and technological challenges continue to make hydrogen a costly option for fuel.

Hydrogen Storage Safety

Safety is a major concern when it comes to storing and transporting hydrogen gas due to its highly flammable nature. If mixed with air, hydrogen can ignite even with a small spark. To store hydrogen safely, special containers and infrastructure are needed, which can add to the overall cost and complexity.

• Compressed Gas Storage: Hydrogen is stored under high pressure, requiring robust and expensive tanks.
• Liquid Hydrogen Storage: Hydrogen is cooled to cryogenic temperatures, which involves complex refrigeration systems.

Implementing these safety measures is crucial but challenging, posing significant hurdles in the widespread adoption of hydrogen as a fuel.