The equilibrium constant, K c, is calculated using molar concentrations. For gas

Question

The equilibrium constant, Kc, is calculated using molar concentrations. For gaseous reactions another form of the equilibrium constant, Kp, is calculated from partial pressures instead of concentrations. These two equilibrium constants are related by the equation

Kp=Kc(RT)n

where R=0.08206 Latm/(Kmol), T is the absolute temperature, and n is the change in the number of moles of gas (sum moles products - sum moles reactants). For example, consider the reaction

N2(g)+3H2(g)2NH3(g)

for which n=2(1+3)=2.

For the reaction

3A(g)+2B(g)C(g)

Kc = 84.6 at a temperature of 371 C .

Calculate the value of Kp.

Express your answer numerically.

Part B

For the reaction

X(g)+3Y(g)3Z(g)

Kp = 2.56×102 at a temperature of 317 C .

Calculate the value of Kc.

Express your answer numerically.

Explanation / Answer

                Given : Reaction

3 A (g) + 2 B(g) --- > C (g)

Kc =84.6 at T = 371 deg C = 371+273.15 = 644.15 K

Calculation of delta n of the reaction.

Delta n = Moles of product – moles of reactant

=1 – 5 = -4

We use following formula

Kp=Kc(RT)n

We use R and value = 0.08206 L atm/ (K.mol)

Kp = 84.6 ( 0.08206 L atm (K mol)1 x 644.15 K)-4

=1.084 E-5

Q. 2
The given reaction is

X (g) + 3 Y (g) --- > 3 Z(g)

Delta n = 3- 4 = -1

2.56 E-2 = Kc ( 0.08206 L atm (K mol)1 x 590.15 K)-1

Kc = 1.23

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