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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: zubinarmase on May 21, 2022, 01:41:19 AM

Title: CO2 Liquid relation with Gas
Post by: zubinarmase on May 21, 2022, 01:41:19 AM

Hello,
I have a doubt about quemistry that I could not do properly the maths that I want.

I work in a company and they have 100% CO2 in a huge gas tank, for welding, 15 bar, -30 degrees.
My company, pays to the company to fill the tank 250 €/TON of CO2, liquid.
But, when the welders do their job, they spent 8 l/minute (gas).

How can i get the properly the money that I spent in imagine 15 minutes of work.

Could you help me?
Title: Re: CO2 Liquid relation with Gas
Post by: Meter on May 21, 2022, 02:09:41 AM
If you assume CO2 to be an ideal gas, you can use the ideal gas law.

Edit: Never mind, I misread the question.
Title: Re: CO2 Liquid relation with Gas
Post by: Borek on May 21, 2022, 03:23:07 AM
Hard to tell exactly not knowing what is the temperature of the gas used. Assuming it is delivered at 8 Lpm at room temperature it is - as Meter wrote - just a trivial application of ideal gas law followed by also a trivial conversion of moles to mas.

Looks to me like a question form the "dimensional analysis" section of a HS book.
Title: Re: CO2 Liquid relation with Gas
Post by: Meter on May 21, 2022, 08:10:13 AM
(https://www.researchgate.net/profile/Miroslaw-Majkut-2/publication/267328310/figure/fig1/AS:392091126517763@1470493217774/A-phase-diagram-for-CO2.png)

From: https://www.researchgate.net/figure/A-phase-diagram-for-CO2_fig1_267328310

So at -30 oC and 15 atm (~1.5 MPa) CO2 is definitely in its liquid phase. If you know the internal volume of the tank, you can calculate to moles. Then 8 l/min would be easy to calculate if you know the pressure of the gas upon expulsion.
Title: Re: CO2 Liquid relation with Gas
Post by: Borek on May 21, 2022, 01:14:40 PM
If you know the internal volume of the tank, you can calculate to moles

My understanding is that OP has the price per mass, so there is no need to know the amount in the tank.
Title: Re: CO2 Liquid relation with Gas
Post by: zubinarmase on May 23, 2022, 12:55:16 AM
Get many ideas from different people and places and also from the internet, I will update once I found the solution, Thank you guys for your help :)