if the gaseous feed to a reactor consists of 30moles of CO, 12 moles of CO2 and 36moles of steam per hour at 800 degrees Celsius and 18moles of H2 per hour. which is the limiting reactant and what...

if the gaseous feed to a reactor consists of 30moles of CO, 12 moles of CO2 and 36moles of steam per hour at 800 degrees Celsius and 18moles of H2 per hour. which is the limiting reactant and what is the fractional conversion of steam? what is the degree of completion of the reaction?

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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The reaction here seems to be Water Gas Shift Reaction, which is given chemically as:

`CO + H_2O<=> CO_2 + H_2`

This reversible reaction is used to generate hydrogen gas from carbon monoxide and water (steam). Sometime, reverse water gas shift reaction is also attempted to generate carbon monoxide or water & oxygen (esp. for space missions).

Here we have various concentrations of all these reactants. Since the chemical equation shows molar equivalency (1 mole CO ~ 1 mole water ~ 1 mole CO2 ~ 1 mole hydrogen), the limiting reactant would be carbon dioxide, since it has only 12 moles (otherwise the reaction may have moved in the reverse direction). Also since carbon monoxide and water is in much higher concentration, the reaction will move forward.

Since the feed of all the reactants is continuous, something interesting will happen.

After 9 moles of reactants (CO and water) have been consumed, their amount remaining would be 21 (= 30-9) moles CO and 27 (=36-9) mole water (or steam). The products' amount would be 21 (12+9) moles CO2 and 27 (=18+9) moles H2. At this point, the reaction would reach a dynamic equilibrium. If the reaction goes forward further, the concentration of reactants on left hand side would increase and it will move in the other direction. 

The fractional conversion of steam would be 9 moles out of 36 moles, i.e. 25% or 0.25.

Since equilibrium is reached, the reaction is complete. 

Hope this helps.

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