Consider the following reaction. A(ag) rhar2 3B(aq) Kc = 4.70 x 10-6 at 500 K If

Question

Consider the following reaction. A(ag) rhar2 3B(aq) Kc = 4.70 x 10-6 at 500 K If a 4.80 M sample of A is heated to 500 K, what is the concentration of B at equilibrium? [B]= M Phosphorus pentachloride decomposes according to the chemical equation PCl5(g) rlhar PCl3(g) KC = 1.80 at 250 degree C A 0.355 mol sample of PCl5(g) is injected into an empty 3.75 L reaction vessel held at 250 degree C. Calculate the concentrations of PCl5(g) and PCl3(g) at equilibrium. [PCl] = M [PCl3] = M At a certain temperature, the Kp for the decomposition of H2S is 0.733. H2S(g) rlhar2 H2(g) + S(g) Initially, only H2S is present at a pressure of 0.287 atm in a closed container. What is the total pressure in the container at equilibrium? atm

Explanation / Answer

Kc=4.7E-6

A<==>3B

4.8.............0

4.8-x..........3x

kc=(3x)3/(4.8-x)

0.0000047(4.8-x)=27x3

27x3+0.0000047x-0.0000226=0

x=0.00942 so at equillibrium

[B]=3x=0.0283M

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Kc=1.8

[PCl5]=0.355moles/3.75L=0.0947M

PCl5 <==>PCl3 + Cl2

0.0947............0.........0

0.0947-x.........x...........x

kc=x2/(0.0947-x)

1.8(0.0947-x)=x2

x2+1.8x-0.1704=0 solve quadratic equation

x=0.09

so at equillibrium

[PCl5]=0.0947-0.09=0.0047M

[PCl3]=x=0.09M

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kp=0.733

H2S<==>H2 + S

0.287...................

0.287-x......x.........x

kp=0.733=x2/(0.287-x)

x2+0.733x-0.2104=0

x=0.2206

so at equillibrium

P(H2S)=0.287-02206=0.0664atm

P(H2)=P(S)=x=0.2206atm

Total pressure=P(H2S)+P(H2)+P(S)=0.0664+0.2206+0.2206=0.5076atm

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