PLEASE HELP ME! The Equilibrium Constant, K c , for the formation of nitrosyl ch

Question

PLEASE HELP ME!

The Equilibrium Constant, Kc, for the formation of nitrosyl chloride, an orange-yellow compound, from nitric oxide and molecular chlorine

                                                2 NO (g)     +     Cl2(g)     ?    2 NOCl (g)

is 6.5 x 104at 35 oC. In a specific experiment, 2.0 x 10-2moles of NO, 8.3 x 10-3moles of Cl2, and 6.8 moles of NOCl are mixed in a 2.0 L flask.  

a.)  Calculate Q for the initial concentrations to determine which direction this equilibrium will have to shift.

b.)  Set up and fill in the I-C-E table for this reaction.

c.)  Write out the equilibrium constant expression (K) and fill in the equilibrium data.

d.)  Solve for x, report both roots that the quadratic formula solution provides, and then conclusively identify the one “correct” root.

e.)  Calculate and report the Equilibrium Concentrations for all reactants and products.

f.)  Is the shift you predict in part (2.a.) above an example of LeChatelier’s Principle? Please explain.

Explanation / Answer

The given reaction

2 NO (g) + Cl2(g) = 2 NOCl (g)

Equilibrium constant Kc = 6.5 * 10^4

Initial concentration = moles/Volume

[NO] = (2.0 * 10^-2)/2 = 0.01 M

[Cl2] = (8.3*10^-3) /2 = 0.00415 M

[NOCl] = 6.8/2 = 3.4 M

Part a

Reaction Quotient

Q = [NOCl]2 / [Cl2] [NO]2

= [3.4]2 / [0.00415] [0.01]2

= 2.786*10^7

Part b

The reaction with ICE TABLE

2 NO (g) + Cl2(g) = 2 NOCl (g)

I 0.01 0.00415 3.4

C - 2x -x +2x

E (0.01-2x) (0.00415-x) (3.4+2x)

Part c

Equilibrium constant expression of the reaction

Kc = [NOCl]2 / [Cl2] [NO]2

6.5 * 10^4 =   [3.4+2x]2 / [0.00415-x] [0.01-2x]2

Part d

Solve for x

(6.5 * 10^4) (0.00415-x) (0.01-2x)2 =   [3.4+2x]2

(269.75 - 65000x) (0.0001 + 4x2 - 0.04x) = 11.56 + 4x2 + 13.6x

0.026975 + 1079x2 - 10.79x - 6.5x - 260000x3 + 2600x2 = 11.56 + 4x2 + 13.6x

- 260000x3 + 3675x2 - 30.89x - 11.533025 = 0

x1 = - 0.0303

x2 = 0.02 + 0.03i

x3 = 0.02 - 0.03i

x2 & x3 are imaginary roots

Correct root x1 = - 0.0303

Negative sign shows that the reaction proceeds in the reverse direction

At equilibrium

[NOCl] = 3.4+2x = 3.4 + 2*(-0.0303) = 3.3394 M

[Cl2] = 0.00415-x = 0.00415 + 0.0303 = 0.03445 M

[NO] = 0.01-2x = 0.01 + 2*0.0303 = 0.0706 M

Reaction Quotient Q > equilibrium constant Kc

Equilibrium shifts to the left

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