15) The equilibrium of PC3 and Cl2 with PCls was studied by placing 1.0 mol of P

Question

15) The equilibrium of PC3 and Cl2 with PCls was studied by placing 1.0 mol of PCs in a 20 liter container. When equilibrium was achieved, there was 0.78 mol of PCis r equilibrium constant for the reaction remaining What is the A) 92 O 16 D) 32 19) The reaction 19) has a value of Kp of 206 at 760 K. If the inátial pressure of ICIs is 2.40 atm, what lis t PCI3 at equilibrium? A) 1.18 atm B) 22.2 atm C 2.42 atm D)235 atm 20) How can the reaction quotient be used to predict the direction of chemical reactions? 20) A) If the reaction quotient is equal to K, reactants are converted to products 5) If the reaction quotient is greater than K, reactants are converted to products. C) If the reaction quotient is less than K, reactants are converted to products D) If the reaction quotient is less than K products are converted to reactants 21) 21) The equilibrium constant for the reaction A misture of gases has the following composition: [NOCI-5.0 10-3 mal/l, INo]-25 10-3 mol/L, and IC21-20 10-3, Is the system at equilibeium? f not, in which direction should the reaction go to achieve equilibrium? A) No, reactants will be converted to products 5) Yes, equihibrium has been achieved Q No, products will be converted to reactants D) No, equilibrium cannot be achieved. The questions that follow are based on the reaction at equilibrium: dW= +172.5 km! Cs).CO2g) g) 22) What would be the effect of decreasing the temperature on the preoeding reaction? 22) - A) The position of the equilibrium would not change. B) The reaction would proceed to the reactant side. O The reaction would proceed to the product side D) Additional information is needed to answer this question. 23) What would be the effect on the preceding reaction of decreasing the volume to original value? A) The reaction would proceed to the reactant side. B) The position of the equailibrium would not change. C The reaction would proceed to the product side. D) Additional information is needed to answer the question.

Explanation / Answer

Q18

First, let us define the equilibrium constant for any species:

The equilibrium constant will relate product and reactants distribution. It is similar to a ratio

The equilibrium is given by

rReactants -> pProducts

Keq = [products]^p / [reactants]^r

For a specific case:

aA + bB = cC + dD

Keq = [C]^c * [D]^d / ([A]^a * [B]^b)

K = [PCl5]/([PCl3][Cl2])

substitute

initially

[PCl5] = 1/2 = 0.5

[PCl3] = 0

[Cl2] = 0

in equilbirium

[PCl5] = 0.5 - x

[PCl3] = 0 + x

[Cl2] = 0 + x

and we know

[PCl5] = 0.5 - x = 0.78/2

x = 0.78/2-0.5 = 0.11

[PCl3] = 0 + x = 0.11

[Cl2] = 0 + x = then

K = [PCl5]/([PCl3][Cl2])

K = (0.78/2) /(0.11*0.11)

K = 32.231

choose D

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