Worksheet: Equilibrium Constants and Pressures

In this worksheet, we will practice converting between partial pressures and equilibrium constants for reactions involving at least one gas.

Q1:

What is the pressure of CO2 in an equilibrium gas mixture containing 0.45 atm of H2, 1.95 atm of HO2, and 0.95 atm of CO at 990C? H()+CO()HO()+CO()atC222Pgggg𝐾=1.6990

Q2:

What is the pressure of BrCl in an equilibrium mixture of Cl2, Br2, and BrCl if the pressure of Cl2 in this mixture is 0.115 atm and the pressure of Br2 is 0.450 atm? Cl()+Br()2BrCl()22Pggg𝐾=4.7×10

  • A 4 . 9 × 1 0 atm
  • B 4 . 1 × 1 0 atm
  • C 2 . 4 × 1 0 atm
  • D20 atm
  • E 5 . 2 × 1 0 atm

Q3:

One of the important reactions in the formation of smog is represented by the following equation. O()+NO()NO()+O()322Pgggg,𝐾=6.0×10 In a gas mixture, the initial partial pressures of O3 and NO are both equal to 1.2×10 atm. The partial pressures of all gases are 1.0 atm under standard conditions. Calculate the partial pressure of O3 in the gas mixture at equilibrium.

  • A 4 . 9 × 1 0 atm
  • B 7 . 9 × 1 0 atm
  • C 3 . 1 × 1 0 atm
  • D 1 . 4 × 1 0 atm
  • E 7 . 1 × 1 0 atm

Q4:

What is the partial pressure of S2 in an equilibrium mixture that results from the decomposition of HS2 with an initial pressure of 0.824 atm? 2HS()2H()+S()222Pggg𝐾=2.2×10 Assume that all pressures in 𝐾P are expressed relative to a standard pressure of 1.00 atm and that changes in the pressure of HS2 are small enough to be neglected.

Q5:

At 25C and 1 atm, the partial pressures in an equilibrium mixture of NO24 and NO2 are 𝑃(NO)=0.70atm24 and 𝑃(NO)=0.30atm2.

Nitrogen dioxide (NO)2 dimerizes to form dinitrogen tetroxide (NO)24. How will the pressures of NO2 and NO24 change if the total pressure increases to 9.0 atm?

  • AThe partial pressure of NO2 will decrease, while that of NO24 will increase.
  • BThe partial pressure of NO2 will increase, while that of NO24 will decrease.
  • CBoth will increase.
  • DBoth will decrease.
  • EThey will both stay the same.

Calculate, to 1 significant figure, the equilibrium partial pressure of NO2 at 9.0 atm and 25C.

Q6:

Consider the reaction between H2 and O2 at 1000 K. Under standard conditions, each species has a partial pressure of 1 atm. If a flask contains 0.500 atm of H2 and 0.500 atm of O2, calculate the partial pressure of hydrogen at equilibrium.

  • A 1 . 6 0 × 1 0 atm
  • B 0.500 atm
  • C 6 . 4 6 × 1 0 atm
  • D 9 . 0 5 × 1 0 atm
  • E 8 . 6 7 × 1 0 atm

Q7:

Liquid NO23 is dark blue at low temperatures, but the color fades and becomes greenish at higher temperatures as the compound decomposes to NO and NO2. At 25C, a value of 𝐾P = 1.91 has been established for this decomposition. If 0.236 moles of NO23 are placed in a 1.52 L vessel at 25C, what is the equilibrium partial pressure of NO()23g?

Q8:

Nitrogen oxides are air pollutants produced by the reaction of nitrogen and oxygen at high temperatures. At 2,000C, the value of the equilibrium constant for the reaction shown is 4.1×10. N()+O()2NO()22ggg Calculate the equilibrium concentration of NO()g in air at 2,000C if [N]2 = 0.036 M and [O]2 = 0.0089 M when equilibrium is reached.

  • A 8 . 1 × 1 0 M
  • B 3 . 6 × 1 0 M
  • C 8 . 8 × 1 0 M
  • D 7 . 8 × 1 0 M
  • E 1 . 3 × 1 0 M

Q9:

Sodium sulfate decahydrate, NaSO·10HO242, dehydrates according to the equation shown. NaSO·10HO()NaSO()+10HO()atC242242Pssg,𝐾=4.08×1025 In the equilibrium constant 𝐾P, partial pressures are defined relative to a standard pressure of 1 atm. Calculate the partial pressure of water vapor at equilibrium with a mixture of NaSO·10HO242 and NaSO4 at 25C.

  • A24.4 atm
  • B 3 . 6 4 × 1 0 atm
  • CNot enough information has been provided.
  • D 4 . 0 8 × 1 0 atm
  • E 4 . 0 8 × 1 0 atm

Q10:

A sample of ammonium chloride was heated in a closed container. Ammonium chloride thermally decomposes according to the equation shown. NHCl()NH()+HCl()43sgg At equilibrium, the pressure of NH()3g was found to be 1.75 atm. Using a standard gas pressure of 1.00 atm, calculate the value of the equilibrium constant 𝐾P for the decomposition at this temperature.

Q11:

Consider the shown reaction. N+O2NO22()()()ggg

The equilibrium constant for this reaction has a value of 2.5×10 at a temperature of 2,400 K. What would be the partial pressure of NO in an equilibrium mixture that is at 2,400 K and contains N2()g at a partial pressure of 0.1 bar and O2()g at a partial pressure of 0.1 bar?

  • A 3 . 5 × 1 0 bar
  • B 7 . 8 × 1 0 bar
  • C 5 . 0 × 1 0 bar
  • D 2 . 5 × 1 0 bar
  • E 2 . 5 × 1 0 bar

Q12:

Nitric oxide (NO) and chlorine react reversibly to form nitrosyl chloride (NOCl) according to the following equation. 2NO()+Cl()2NOCl()ggg2 In a gas mixture at equilibrium, the partial pressures of NO, Cl2, and NOCl are 0.050 atm, 0.30 atm, and 1.2 atm respectively. Using a standard gas pressure of 1.0 atm, calculate the equilibrium constant 𝐾P for this reaction.

  • A 1 . 9 × 1 0
  • B 5 . 2 × 1 0
  • C 0 . 0 9 6 × 1 0
  • D 1 . 0 × 1 0
  • E 0 . 0 8 0 × 1 0

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