Question

select the formula of a particle that can exist as a gas.
□ nacl
□ xe
□ h₂
□ h₂o
□ hg
□ fe

Explanation:

Step1: Analyze each substance's state

• NaCl: Ionic compound, solid at room temp, high melting/boiling, not gas.
• Xe: Noble gas, exists as gas (monatomic) at room temp.
• H₂: Diatomic gas, gaseous at room temp.
• H₂O: Liquid at room temp (can be vapor/gas, but let's check others).
• Hg: Liquid metal, not gas.
• Fe: Solid metal, not gas.

Step2: Confirm gaseous substances

Xe (noble gas, gaseous) and H₂ (diatomic gas) are gases. NaCl is solid, H₂O liquid (vapor is gas but let's see options), Hg liquid, Fe solid. So Xe and H₂ (and H₂O vapor, but as a particle, H₂ and Xe are gases. Wait, the question is "can exist as a gas"—so Xe (gas), H₂ (gas), H₂O can be gas (steam), but let's check the options. Wait, the options: Xe is a noble gas (gas), H₂ is hydrogen gas, H₂O can be gas (but at room temp it's liquid, but it can exist as gas). Wait, but the question is "select the formula"—so possible correct ones: Xe, H₂, and H₂O can be gas, but let's check standard states.

Wait, Xe: gaseous at STP. H₂: gaseous at STP. H₂O: liquid at STP, but can be gas (vapor). NaCl: solid. Hg: liquid. Fe: solid. So the correct options are Xe, H₂, and H₂O (but H₂O is liquid at STP, but can exist as gas). Wait, but the question is "can exist as a gas"—so all three? But let's check the options. Wait, the user's question is to select the formula. Let's re-express:

• NaCl: solid (no)
• Xe: gas (yes)
• H₂: gas (yes)
• H₂O: can be gas (yes, as steam)
• Hg: liquid (no)
• Fe: solid (no)

But maybe the question expects Xe, H₂, and H₂O? Wait, but let's check standard conditions. At STP (25°C, 1 atm), Xe is gas, H₂ is gas, H₂O is liquid (but at higher temp, gas). So the substances that can exist as gas (under some conditions) are Xe, H₂, and H₂O. But maybe the intended answers are Xe and H₂ (and H₂O). Wait, but let's see the options. Let's confirm:

Xe: noble gas, gaseous.

H₂: hydrogen gas, gaseous.

H₂O: water vapor is gas, so it can exist as gas.

But maybe the question is about standard state? No, "can exist as a gas"—so any condition. So Xe, H₂, H₂O are correct. But let's check the options. Wait, the user's question is to select the formula. So possible correct options: Xe, H₂, and H₂O. But let's see the original options. Let's list:

• NaCl: solid (no)
• Xe: gas (yes)
• H₂: gas (yes)
• H₂O: can be gas (yes)
• Hg: liquid (no)
• Fe: solid (no)

So the correct ones are Xe, H₂, and H₂O. But maybe the question expects Xe and H₂ (since H₂O is liquid at room temp, but it can be gas). Wait, but the question is "can exist as a gas"—so yes, H₂O can exist as gas (steam). But maybe the intended answers are Xe and H₂. Let's check:

Xe is a noble gas (gaseous), H₂ is hydrogen gas (gaseous), H₂O is water (can be gas). So the correct options are Xe, H₂, and H₂O. But let's see the options given. So the answer would be Xe, H₂, and H₂O (but maybe the question has multiple correct, but let's check the original problem. Wait, the user's image shows checkboxes, so multiple selection. So the correct options are:

Xe (B. Xe), H₂ (C. H₂), and H₂O (D. H₂O). Wait, the options are:

• NaCl (A)
• Xe (B)
• H₂ (C)
• H₂O (D)
• Hg (E)
• Fe (F)

So the correct ones are B, C, D. But let's confirm:

• Xe: gas (yes)
• H₂: gas (yes)
• H₂O: can be gas (yes)
• NaCl: solid (no)
• Hg: liquid (no)
• Fe: solid (no)

So the answer is B. Xe, C. H₂, D. H₂O. But maybe the question considers H₂O as liquid, but it can exist as gas. So the correct options are Xe, H₂, and H₂O.

Answer:

B. Xe, C. H₂, D. H₂O