The correct statements among (I) to (IV) regarding H2 as a fuel are :
I. It produces less pollutants

Q: Why does a hydrogen cylinder weigh so much more than a petrol tank?

Hydrogen is a very low-density gas. To store enough energy, it must be highly compressed, which requires thick, heavy steel or composite cylinders, making the overall storage system much heavier than a simple plastic or thin metal petrol tank.

Q: What is $NaNi_5$ and how does it store hydrogen?

$NaNi_5$ is a metal alloy that can absorb hydrogen gas into the microscopic spaces (interstices) of its crystal lattice, forming a metal hydride. It acts like a sponge for hydrogen.

Q: If hydrogen has such high energy per gram, why isn't it used everywhere?

While its energy per gram is high, its energy per *volume* is very low. Storing and transporting it requires heavy cylinders or cryogenic temperatures, which is currently expensive and technologically challenging.

Q: Is hydrogen completely pollution-free?

The combustion of hydrogen itself produces only water, which is pollution-free. However, if the hydrogen is produced using fossil fuels (like steam methane reforming), the *production* process can generate pollution.

Q: Why did the question mention liquid dihydrogen?

Liquid dihydrogen is used to maximize energy density by volume, especially in applications like rocket fuel. It requires extremely low temperatures (-253 °C) to remain liquid.

Question

The correct statements among (I) to (IV) regarding $H_2$ as a fuel are :
I. It produces less pollutants than petrol.
II. A cylinder of compressed dihydrogen weights ~30 times more than a petrol tank producing the same amount of energy.
III. Dihydrogen is stored in tanks of metal alloys like $NaNi_5$.
IV. On combustion, values of energy released per gram of liquid dihydrogen and LPG are 50 and 142 kJ, respectively.

Options:

(A) I, II and III only

(B) II, III and IV only

(C) II and IV only

(D) I and III only

Sigma Percentile · Accepted Answer

### The Future of Fuel: Evaluating Hydrogen

Hydrogen is often touted as the ultimate clean energy source. But is it really that simple? Let's dive into the properties of dihydrogen ($H_2$) as a fuel and evaluate the four statements given in the problem.

### The Clean Energy Promise (Statement I)

When we burn petrol, we get a nasty cocktail of carbon dioxide, carbon monoxide, and nitrogen oxides. But what happens when we burn hydrogen? The only byproduct is water ($H_2O$).

It is a 100% pollution-free fuel. So, the first statement is absolutely correct.

### The Weight Dilemma (Statement II)

If hydrogen is so great, why aren't all our cars running on it? The catch is storage. Hydrogen is an incredibly light gas.

To store enough of it to match the energy of a full petrol tank, we have to compress it under immense pressure. The heavy steel cylinders required for this make the entire setup about 30 times heavier than a standard petrol tank. So, statement II is a harsh reality, but it is correct.

### The Metal Sponge Solution (Statement III)

To solve the weight and volume problem, scientists have developed clever storage methods. Instead of just compressing the gas, they use metal alloys like $NaNi_5$ (sodium pentanickel).

These alloys act like a sponge, absorbing hydrogen gas into their crystal lattice. This allows for safe and compact storage of hydrogen in small quantities. Statement III is correct.

### The Energy Champion (Statement IV)

Finally, let's talk about energy. The calorific value of a fuel tells us how much energy it releases per gram.

Liquid hydrogen is the undisputed champion here, releasing a massive $142 	ext{ kJ g}^{-1}$. In comparison, LPG releases only about $50 	ext{ kJ g}^{-1}$. The fourth statement claims the opposite, swapping the values. Therefore, statement IV is incorrect.

### Conclusion

Statements I, II, and III are correct, while statement IV is incorrect. This makes option (a) the right answer. Hydrogen has incredible potential, but mastering its storage is the key to unlocking the hydrogen economy!

Select Answer:

Visualized Solution

$H_{2}$ as a Fuel

Statement I: Pollution

Statement II: Weight Comparison

Statement III: Metal Alloy Storage

Statement IV: Energy Released

Final Conclusion

The Sigma Insight: Hydrogen, Hydrides and Water

The Future of Fuel

The Clean Energy Promise (Statement I)

The Weight Dilemma (Statement II)

The Metal Sponge Solution (Statement III)

The Energy Champion (Statement IV)

Conclusion

Similar Questions

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