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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: JArchy123 on December 22, 2021, 08:30:02 PM

Title: Determining what reaction is more favourable.
Post by: JArchy123 on December 22, 2021, 08:30:02 PM
I am doing a project at the minute with three reactions occurring. The reactions include:

CH4 + H2O --> CO + 3H2
CO + H20 <--> CO2 + H2
CH4 + 2H2O <--> CO2 + 4H2

My lecturer and I have assumed the first reaction has a CH4 conversion of 95% with the flow rate of both the CH4 and H2O being 134.4753 mol/s. If I have the 95% conversion, I am wondering how much H2O would be provided to each of the other two steps; that is assuming the other 5% of the CH4 is going to the other steps.
Title: Re: Determining what reaction is more favourable.
Post by: Orcio_87 on December 23, 2021, 09:13:08 AM
More favorable reaction is the one with a higher reaction constant (K).
Title: Re: Determining what reaction is more favourable.
Post by: Corribus on December 23, 2021, 01:27:29 PM
Quote from: JArchy123 on December 22, 2021, 08:30:02 PM
My lecturer and I have assumed the first reaction has a CH4 conversion of 95% with the flow rate of both the CH4 and H2O being 134.4753 mol/s.
Why would you assume this? And what is the flow rate related to? There doesn't seem like enough information about your experiment to answer this question.
Title: Re: Determining what reaction is more favourable.
Post by: JArchy123 on December 23, 2021, 01:59:00 PM
My colleagues and I calculated a mass balance for the conversion of CH4 to CO and H2 for 95% conversion with the flow rates determined for this preliminary mass balance. In addition, I determined the equilibrium constant (K) to be 0.00968 (3.sf) for the second reaction step and 1.27 * 10^10 (3.sf) for the third step.
Title: Re: Determining what reaction is more favourable.
Post by: Borek on December 23, 2021, 06:39:09 PM
Quote from: Orcio_Dojek on December 23, 2021, 09:13:08 AM
More favorable reaction is the one with a higher reaction constant (K).

Not necessarily, kinetics might favor the less thermodynamically likely one.
Title: Re: Determining what reaction is more favourable.
Post by: JArchy123 on December 24, 2021, 09:54:23 AM
How would I then determine which one is more favourable?
Title: Re: Determining what reaction is more favourable.
Post by: Corribus on December 24, 2021, 11:15:10 AM
The first step is defining what you mean by "more favorable".
Title: Re: Determining what reaction is more favourable.
Post by: Orcio_87 on December 24, 2021, 03:13:22 PM
Quote
The first step is defining what you mean by "more favorable".
At given time (5, 10 or 30 min.) 95 % of CH4 was converted to CO and H2. If given more time, rest of the H2O will react with the CO or rather with the remaining 5 % of CH4 ? (he is asking about yield of the two next reactions).
Title: Re: Determining what reaction is more favourable.
Post by: Corribus on December 26, 2021, 05:38:16 PM
He asked what is more favorable. "Favorable" in chemistry is not defined without additional context. Thermodynamic and kinetic favorability are two different things.