Chemical equilibrium worksheet with answers

Free printable Chemical equilibrium worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
PCl5​0.3mol/L⇌PCl3​0.1mol/L+Cl2​0.15mol/LKc​ = ?

For the reaction PCl5 ⇌ PCl3 + Cl2, the equilibrium concentrations are [PCl5] = 0.3 mol/L, [PCl3] = 0.1 mol/L, [Cl2] = 0.15 mol/L. Find the equilibrium constant Kc.

[PCl5] = 0.3[PCl3] = 0.1[Cl2] = 0.15
Kc =
2.Easy
N2​0.1mol/L+3H2​0.05mol/L⇌2NH3​0.5mol/LKc​ = ?

For the reaction N2 + 3H2 ⇌ 2NH3, the equilibrium concentrations are [N2] = 0.1 mol/L, [H2] = 0.05 mol/L, [NH3] = 0.5 mol/L. Find the equilibrium constant Kc.

[N2] = 0.1[H2] = 0.05[NH3] = 0.5
Kc =
3.Medium
H2​I2​HII0.80.80C−x−x+2xE0.8 − x0.8 − x2x

0.8 mol/L of H₂ and 0.8 mol/L of I₂ are put in a container and react: H₂ + I₂ ⇌ 2HI, with Kc = 54. Find the equilibrium concentration [HI].

[H₂]₀ = [I₂]₀ = 0.8 mol/LKc = 54
[HI] = mol/L
4.Medium
H2​I2​HII0.10.10C−x−x+2xE0.1 − x0.1 − x2x

0.1 mol/L of H₂ and 0.1 mol/L of I₂ are put in a container and react: H₂ + I₂ ⇌ 2HI, with Kc = 50. Find the equilibrium concentration [HI].

[H₂]₀ = [I₂]₀ = 0.1 mol/LKc = 50
[HI] = mol/L
5.Hard
PCl5​PCl3​Cl2​I100C−x+x+xE1 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.5 at the reaction temperature. A container starts with 1 mol/L of PCl₅ only. Find the equilibrium concentration [Cl2].

[PCl₅]₀ = 1 mol/LKc = 0.5
[Cl2] = mol/L
6.Hard
PCl5​PCl3​Cl2​I0.400C−x+x+xE0.4 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.02 at the reaction temperature. A container starts with 0.4 mol/L of PCl₅ only. Find the equilibrium concentration [PCl5].

[PCl₅]₀ = 0.4 mol/LKc = 0.02
[PCl5] = mol/L

Answer key

  1. 1. Kc = 0.05
  2. 2. Kc = 20000
  3. 3. [HI] = 1.258 mol/L
  4. 4. [HI] = 0.1559 mol/L
  5. 5. [Cl2] = 0.5 mol/L
  6. 6. [PCl5] = 0.32 mol/L

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