Tiantai University Tutorial, Chapter 1: Material Balance, Example on Absorption on page P9
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In solving this problem, to calculate the number of moles n of inert gas in the flow rate of the mixed gas per hour, is it n=1000/22.4×273/(273+20)×(1-0.05)? Why convert? I’m suddenly confused; please ask an expert to help answer, thank you!
Is n the number of moles under standard conditions? Why not under operating conditions? What is the meaning of this conversion here? It’s a bit blurry! Experts, please give me some guidance!
Although we still didn’t receive any notice of the exam in 2015, we can’t give up completely! One still has to maintain the habit of continuing to learn; it can’t be ignored. Before, I only knew the surface aspects but not the underlying reasons, and every time I read something, I make new discoveries!
Although the formula above can be derived, why isn’t n equal to 1000/22.4x(1-0.05)?
For real gases, if the pressure does not exceed 10 atmospheres, they can still be treated as ideal gases. Thus, p0*22.4=1*R*273..........(1) and p0*1000=nR*(273+20)..(2). Therefore, n=1000/22.4*(273/273+20); it is important to have a thorough understanding of the basic concepts!
Thank you for your answer. In the absorption chapter, many calculations involve directly using the molar amount of inert gases, without any conversions being made! Under what circumstances is such calculation necessary? Does it depend on whether the operating pressure exceeds 1 MPa? How is it calculated when it exceeds 1 MPa? On page P6, under standard conditions (0 degrees Celsius, 0.10133 MPa), the volume of 1 kmol of gas is 22.4 m3. Thus, a formula for the volume of gas at general pressure and temperature can be calculated as V = 22.4n×(273 + t)/273 × 0.10133/p. Here, does n refer to the number of moles under standard conditions? (This formula can be used to derive the number of moles of n at a pressure of 1 MPa; please help me understand this further, thank you.)
Here, n refers to the molar amount in the actual state! This formula represents the molar volume under actual conditions, equivalent to that under standard conditions! Don’t memorize formulas by rote! One must learn to derive, otherwise mistakes will be made! If the pressure exceeds 10 atmospheres, it should be treated as an ideal gas! The compressibility factor has been introduced! PV=n*ZRT
Thank you so much for your patient answers! It feels like there’s a huge gap between me and them; I’m far behind. I need to keep reading and learning more! I understood a problem and the theoretical knowledge! Thank you!
1000 cubic units represents the volume under actual conditions; to convert this to the number of moles, the ideal gas law can be used, namely n=PV/RT. Alternatively, the fact that 1 mole of gas occupies 22.4 L under standard conditions can also be utilized for the conversion