Q20 of 73 Page 224

One of the reaction that takes place in producing steel from iron ore is the reduction of iron(II) oxide by carbon monoxide to give iron metal and CO2.

FeO (s) + CO (g) ⇌ Fe (s) + CO2 (g); Kp = 0.265 atm at 1050K


What are the equilibrium partial pressures of CO and CO2 at 1050 K if the initial partial pressures are: = 1.4 atmand = 0.80 atm?

The given reaction is:


The reaction quotient (Qp) measures the partial pressures of products and reactants present during a reaction at a particular point in time. It also indicates the direction in which the reaction is going to proceed.


Here,


And Kp=0.265


Since Qp>Kp, it indicates that the reaction will move in the backward direction to attain equilibrium. This means that the partial pressure of CO2 will decrease and the partial pressure of CO will increase by the same amounts. If the partial pressure of CO2 will decrease by p atm, the partial pressure of CO will increase by p atm.


Hence, and


Equilibrium pressure constant (Kp) is defined as a number that expresses the relationship between the partial pressures of products and reactants present at equilibrium in a reversible chemical reaction at a given temperature.


Therefore,



0.371 + 0.265p = 0.8 – p


1.265p = 0.429


p = 0.339 atm




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18

Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as:

CH3COOH (l) + C2H5OH (l) ⇌CH3COOC2H5 (l) + H2O (l)


(i) Write the concentration ratio (reaction quotient), Qc, for this reaction (note: water is not in excess and is not a solvent in this reaction)


(ii) At 293 K, if one starts with 1.00 mol of acetic acid and 0.18 mol of ethanol, there is 0.171 mol of ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant.


(iii) Starting with 0.5 mol of ethanol and 1.0 mol of acetic acid and maintaining it at 293 K, 0.214 mol of ethyl acetate is found after sometime. Has equilibrium been reached?

 19

A sample of pure PCl5 was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of PCl5 was found to be 0.5 × 10–1 mol L–1. If value of Kc is 8.3 × 10–3, what are the concentrations of PCl3 and Cl2 at equilibrium?

PCl5 (g) ⇌ PCl3 (g) + Cl2(g)

 21

Equilibrium constant, Kcfor the reaction

N2 (g) + 3H2 (g) ⇌ 2NH3 (g) at 500 K is 0.061


At a particular time, the analysis shows that composition of the reaction mixture is 3.0 mol L–1 N2, 2.0 mol L–1 H2 and 0.5 mol L–1 NH3. Is the reaction at equilibrium?


If not in which direction does the reaction tend to proceed to reach equilibrium?

 22

Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:

2BrCl (g) ⇌ Br2 (g) + Cl2 (g) for which Kc= 32 at 500 K. If initially pure BrCl is present at a concentration of 3.3 × 10–3 mol L–1, what is its molar concentration in the mixture at equilibrium?