Which of the following reactions has Kp = Kc?
Note: Multiple answers are allowed.
Question 3Select one or more:
a.
H2(g) + Cl2(g) ⇌ 2 HCl(g)
b.
2 SO3(g) ⇌ 2 SO2(g) + O2(g)
c.
2 NO(g) + 2 CO(g) ⇌ N2(g) + 2 CO2(g)
d.
N2O4(g) ⇌ 2 NO2(g)
e.
CO2(g) + H2(g) ⇌ CO(g) + H2O(g)
b. 2 SO3(g) ⇌ 2 SO2(g) + O2(g)
c. 2 NO(g) + 2 CO(g) ⇌ N2(g) + 2 CO2(g)
In order to determine which reactions have Kp = Kc, we need to understand the difference between Kp and Kc.
Kp is the equilibrium constant expressed in terms of partial pressures of the gases involved in the reaction. On the other hand, Kc is the equilibrium constant expressed in terms of the concentrations (molarities) of the reactants and products.
To find the answer, we need to compare the balanced equations of the given reactions to see if the stoichiometric coefficients and the number of moles of reactants and products are the same.
a. H2(g) + Cl2(g) ⇌ 2 HCl(g)
This reaction has a different number of moles on each side of the equation, so Kp does not equal Kc for this reaction.
b. 2 SO3(g) ⇌ 2 SO2(g) + O2(g)
This reaction has the same number of moles on each side of the equation, so Kp equals Kc for this reaction.
c. 2 NO(g) + 2 CO(g) ⇌ N2(g) + 2 CO2(g)
This reaction has the same number of moles on each side of the equation, so Kp equals Kc for this reaction.
d. N2O4(g) ⇌ 2 NO2(g)
This reaction has a different number of moles on each side of the equation, so Kp does not equal Kc for this reaction.
e. CO2(g) + H2(g) ⇌ CO(g) + H2O(g)
This reaction has a different number of moles on each side of the equation, so Kp does not equal Kc for this reaction.
Therefore, the reactions b and c have Kp = Kc.
To determine which of the given reactions have Kp = Kc, we need to understand the difference between Kp and Kc.
Kp is the equilibrium constant expressed in terms of partial pressures, while Kc is the equilibrium constant expressed in terms of molar concentrations.
To compare Kp and Kc, we need to know the relationship between these two values. For a generic balanced equation:
aA + bB ⇌ cC + dD
The relationship between Kp and Kc is given by:
Kp = Kc(RT)^(Δn)
Where Δn = (c + d) - (a + b), R is the ideal gas constant, and T is the temperature in Kelvin.
Now, for Kp to equal Kc, the value of Δn must be zero. This means that the number of moles of gas on the product side is equal to the number of moles of gas on the reactant side.
Let's analyze each reaction given and determine if Kp = Kc:
a. H2(g) + Cl2(g) ⇌ 2 HCl(g)
In this reaction, there is a decrease in the number of moles of gas (2 - 1 - 1 = 0). Therefore, Kp = Kc.
b. 2 SO3(g) ⇌ 2 SO2(g) + O2(g)
In this reaction, there is no change in the number of moles of gas (0 - 0 - 1 = -1). Therefore, Kp ≠ Kc.
c. 2 NO(g) + 2 CO(g) ⇌ N2(g) + 2 CO2(g)
In this reaction, there is an increase in the number of moles of gas (1 - 2 - 0 = -1). Therefore, Kp ≠ Kc.
d. N2O4(g) ⇌ 2 NO2(g)
In this reaction, there is a decrease in the number of moles of gas (2 - 1 = 1). Therefore, Kp ≠ Kc.
e. CO2(g) + H2(g) ⇌ CO(g) + H2O(g)
In this reaction, there is no change in the number of moles of gas (1 - 1 = 0). Therefore, Kp = Kc.
Based on the analysis, the reactions that have Kp = Kc are:
a. H2(g) + Cl2(g) ⇌ 2 HCl(g)
e. CO2(g) + H2(g) ⇌ CO(g) + H2O(g)
So the correct answers are a and e.