Video Transcript
Find the value of 𝐾 𝑝 for the
reversible reaction two X gas is in equilibrium with Y gas plus Z gas. The partial pressures are as
follows. 𝑝 X equals 50 kilopascals. 𝑝 Y equals 25 kilopascals. 𝑝 Z equals 25 kilopascals. Give your answer to two decimal
places.
𝐾 𝑝 is the equilibrium constant
for partial pressures. The equilibrium constant for
partial pressures is the ratio between the partial pressures of the products and
reactants at equilibrium. Let’s consider a generic reaction
equation where the lowercase letters represent stoichiometric coefficients and the
uppercase letters represent chemical formulas. The 𝐾 𝑝 of this reaction can be
calculated by dividing the partial pressures of the products by the partial
pressures of the reactants, where each individual partial pressure is raised to the
power of the respective stoichiometric coefficient.
We can apply our understanding to
the provided chemical equation to construct an expression for the equilibrium
constant for partial pressures for this reaction. We find that 𝐾 𝑝 is equal to the
partial pressure of Y times the partial pressure of Z divided by the partial
pressure of X squared. We are given the partial pressures
of X, Y, and Z. We can substitute these values into
the equation for 𝐾 𝑝. 50 kilopascals squared is 2500
squared kilopascals. We can see that all of the
kilopascal units will cancel. Thus, 𝐾 𝑝 will be a unitless
value. Performing the calculation gives us
a value of 0.25. This answer is already given to two
decimal places.
Therefore, the equilibrium constant
for partial pressures for the given reaction is 0.25.
