[ooiuniscience]

An electrolysis reaction to produce hydrogen and oxygen in a reactor. Initial headspace pressure is 1atm and the total headspace volume is 5ml and this headspace is saturated with 5 ml of nitrogen gas. After reaction, the pressure is measure to be 1.5 atm. Can i calculate the volume of H2 gas and O2 gas produced using Boyle's Law or any gas law?

Thanks if you able to solve on this issue.

Doubful Jeff

[Borek]

This is trivial stoichiometry. What is sum of the partial pressures of the gases produced? What is their expected ratio?

[ooiuniscience]

This is trivial stoichiometry. What is sum of the partial pressures of the gases produced? What is their expected ratio?

Hi Borek,

The ratio of gas inside headspace is nitrogen: hydrogen: Oxygen = 1: 10: 5. Can we solve this question without any data of partial pressures of the gases produced?

[Borek]

The ratio of gas inside headspace is nitrogen: hydrogen: Oxygen = 1: 10: 5.

No. You are right about hydrogen:oxygen being 2:1, but the nitrogen part i wrong. Do you know Avogadro's hypothesis? Dalton's law?

Can we solve this question without any data of partial pressures of the gases produced?

Depends on what possible other information you have. Question as worded requires some assumptions, otherwise it can be solved at all.

[ooiuniscience]

The ratio of gas inside headspace is nitrogen: hydrogen: Oxygen = 1: 10: 5.

No. You are right about hydrogen:oxygen being 2:1, but the nitrogen part i wrong. Do you know Avogadro's hypothesis? Dalton's law?

Can we solve this question without any data of partial pressures of the gases produced?

Depends on what possible other information you have. Question as worded requires some assumptions, otherwise it can be solved at all.

Hi Borek,

I know Avogadro & Dalton's law but dunno how to apply them in the question.

I only assume the condition obey ideal gas law condition.

[Borek]

I know Avogadro & Dalton's law but dunno how to apply them in the question.

If you had 1 atm of a gas, and now you you have 1.5 atm, what is the partial pressure of the added gasses?

[ooiuniscience]

I know Avogadro & Dalton's law but dunno how to apply them in the question.

If you had 1 atm of a gas, and now you you have 1.5 atm, what is the partial pressure of the added gasses?

Hi Borek,

Partial pressure of added gas is 0.5 atm

[Borek]

Partial pressure of added gas is 0.5 atm

So at 0.5 atm you have 5 mL of 2:1 hydrogen and oxygen mixture. This is almost a ready answer.

[ooiuniscience]

Partial pressure of added gas is 0.5 atm

So at 0.5 atm you have 5 mL of 2:1 hydrogen and oxygen mixture. This is almost a ready answer.

Hi Borek,

Thanks for the hint give

5 ml that you tell me refer to headspace volume or sum of the gases (consist of N2:H2:O2)?

The increment of 0.5atm is due to the H2 gas:O2 gas = 2:1. So the pressure of H2 gas is 0.5/3 atm while that of O2 gas is 0.5/3 (2) atm. But this only give pressure  & doesnt give volume of H2 & O2


Now i know.

[ooiuniscience]

An electrolysis reaction to produce hydrogen and oxygen in a reactor. Initial headspace pressure is 1atm and the total headspace volume is 5ml and this headspace is saturated with 5 ml of nitrogen gas. After reaction, the pressure is measure to be 1.5 atm. Can i calculate the volume of H2 gas and O2 gas produced using Boyle's Law or any gas law?

Thanks if you able to solve on this issue.

Doubful Jeff

My friend told me to use P1V1=P2V2 where P1 is atm pressure, V1 is volume of headspace or volume of N2 gas; P2 is pressure after H2 & O2 gas is generated & V2 is final volume of gas O2 & H2 generated. After substitute, 1(5)=1.5V2 and i get V2 = 3.33. It seems weird because headspace volume is fixed to be 5ml. I strongly no agree with her point of view. Any respected teacher have an idea to solve this?

[Borek]

The increment of 0.5atm is due to the H2 gas:O2 gas = 2:1. So the pressure of H2 gas is 0.5/3 atm while that of O2 gas is 0.5/3 (2) atm. But this only give pressure  & doesnt give volume of H2 & O2

First of all: if you know partial pressure and total volume of a gas, you can calculate number of moles from PV=nRT, then you can convert it back to the partial volume for any given pressure/temperature.

But there is no need for that. I asked you if you know Dalton's law and Avogadro hypothesis - they not only tell you how to calculate partial pressures of the gases present, if combined with the ideal gas law they also tall you how to calculate partial volumes. If you have a volume V of a gas mixture, and partial pressure of the gas X in this mixture is P_x, and the total pressure is P, partial volume of the gas is [itex]\frac {P_x} P \times V[/itex]. Actually it will yield the same result your friend got (and not without a reason).

i get V2 = 3.33. It seems weird because headspace volume is fixed to be 5ml.

That would mean the only answer that you are ready to accept is that hydrogen volume is 5 mL and oxygen volume is 5 mL (at the same time you will probably not accept this answer for other reasons). Looks like you are confusing yourself by not differentiating between volume and partial volume.

[ooiuniscience]

The increment of 0.5atm is due to the H2 gas:O2 gas = 2:1. So the pressure of H2 gas is 0.5/3 atm while that of O2 gas is 0.5/3 (2) atm. But this only give pressure  & doesnt give volume of H2 & O2

First of all: if you know partial pressure and total volume of a gas, you can calculate number of moles from PV=nRT, then you can convert it back to the partial volume for any given pressure/temperature.

But there is no need for that. I asked you if you know Dalton's law and Avogadro hypothesis - they not only tell you how to calculate partial pressures of the gases present, if combined with the ideal gas law they also tall you how to calculate partial volumes. If you have a volume V of a gas mixture, and partial pressure of the gas X in this mixture is P_x, and the total pressure is P, partial volume of the gas is [itex]\frac {P_x} P \times V[/itex]. Actually it will yield the same result your friend got (and not without a reason).

i get V2 = 3.33. It seems weird because headspace volume is fixed to be 5ml.

That would mean the only answer that you are ready to accept is that hydrogen volume is 5 mL and oxygen volume is 5 mL (at the same time you will probably not accept this answer for other reasons). Looks like you are confusing yourself by not differentiating between volume and partial volume.

Hi Borek,

Thanks for your input. Try to digest now...