Relative volume of combusted hydrogen

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Discussion Overview

The discussion revolves around the expected volume of steam produced from the combustion of Brown's gas at a specified temperature and pressure. Participants explore various conditions and assumptions related to the combustion process, including the nature of the container and the behavior of gases before and after combustion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Bob inquires about the expected volume of steam from igniting a volume of Brown's gas at 20°C and 1 atm.
  • Some participants suggest that the volume may remain unchanged in a sufficiently strong container, but they request clarification on the conditions.
  • One participant specifies that the container has a freely-moving piston of negligible mass, prompting further discussion on the scenario's details.
  • Another participant raises questions about the moles of gas before and after combustion and whether the reaction occurs at constant temperature or in an insulated system.
  • Concerns are expressed regarding the safety of conducting combustion experiments, particularly for inexperienced individuals.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the expected volume of steam produced, as multiple competing views and conditions are proposed. The discussion remains unresolved with various assumptions and scenarios being explored.

Contextual Notes

Limitations include the lack of specific assumptions about the combustion process, the dependence on the definitions of the system's conditions, and unresolved details regarding the behavior of gases in the described scenario.

Who May Find This Useful

This discussion may be of interest to individuals studying combustion processes, gas behavior in thermodynamic systems, or those involved in experimental physics and chemistry.

bobbyg
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Hi,

If I had a volume of Brown's gas at 20°C / 1atm, what would the expected volume [of the resultant steam] be immediately after it was ignited?

Thanks!
Bob
 
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bobbyg said:
If I had a volume of Brown's gas at 20°C / 1atm, what would the expected volume [of the resultant steam] be immediately after it was ignited?

In a sufficiently strong container it would remain unchanged. Please specify the conditions.
 
DrStupid said:
In a sufficiently strong container it would remain unchanged. Please specify the conditions.
The container is solid, with a freely-moving piston of negligible mass
 
bobbyg said:
The container is solid, with a freely-moving piston of negligible mass
You will want to nail the scenario down more tightly than that.

For instance, do you want the steam to more or less freely (and adiabatically) expand until it has reached ambient pressure? This, while doing work on the piston against the force of ambient pressure on its other side?

Oh... and is this homework by any chance?
 
How many moles of gas are there before combustion? How many moles of gas are they after combustion? Is the reaction assumed to take place at constant temperature, or is the system insulated?
 
Edit: don't worry. I will just try some physical experiments. Thanks for taking the time to reply
 
Last edited:
bobbyg said:
Edit: don't worry. I will just try some physical experiments.

"Don't worry" and "just try some physical experiments" with Brown's gas don't fit together.
 
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"Don't worry" also does not go well with combustion experiments performed by inexperienced students, especially if it is hydrogen. I am currently assisting with a combustion course and these kind of questions (e.g. computing volume expansion of a combustion process at constant pressure ) are covered in the second lecture.
My advice as a professional combustion researcher to you is: do not do combustion experiments.
 

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