Equipment: nitrous oxide critical temperature: practice question

A Anaesthesia question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anaesthesia · Equipment: nitrous oxide critical temperature

Sample item

Nitrous oxide in a cylinder exists as a liquid in equilibrium with vapour because of which property?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Its critical temperature of 36.5 degrees C is above room temperature

A substance can be liquefied by pressure alone below its critical temperature. Nitrous oxide has a critical temperature of 36.5 degrees C, so it is stored as a liquid with vapour above it, and the pressure gauge stays constant until the liquid is exhausted. Cylinder contents are therefore assessed by weight.

Option by option

  • A. It is stored at 1 atmosphere

    It is stored at high pressure.

  • B. Its critical temperature of 36.5 degrees C is above room temperature (correct)

    Correct. A critical temperature above ambient allows liquefaction under pressure.

  • C. It is an inert gas

    Nitrous oxide is not inert.

  • D. Its critical temperature is below zero

    Oxygen has a critical temperature below zero and stays as a gas.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is B, Its critical temperature of 36.5 degrees C is above room temperature. A substance can be liquefied by pressure alone below its critical temperature.

Why is "It is stored at 1 atmosphere" not the answer?

It is stored at high pressure.

Why is "It is an inert gas" not the answer?

Nitrous oxide is not inert.

Why is "Its critical temperature is below zero" not the answer?

Oxygen has a critical temperature below zero and stays as a gas.

What concept does this question test?

It tests Equipment: nitrous oxide critical temperature in Anaesthesia. Nitrous oxide has a critical temperature of 36.5 degrees C, so it is stored as a liquid with vapour above it, and the pressure gauge stays constant until the liquid is exhausted. Cylinder contents are therefore assessed by weight.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Equipment: nitrous oxide critical temperature?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.