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​0.25mol/L⇌PCl3​0.05mol/L+Cl2​0.4mol/LKc​ = ?

For the reaction PCl5 ⇌ PCl3 + Cl2, the equilibrium concentrations are [PCl5] = 0.25 mol/L, [PCl3] = 0.05 mol/L, [Cl2] = 0.4 mol/L. Find the equilibrium constant Kc.

[PCl5] = 0.25[PCl3] = 0.05[Cl2] = 0.4
Kc =
2.Easy
H2​0.4mol/L+I2​0.12mol/L⇌2HI0.25mol/LKc​ = ?

For the reaction H2 + I2 ⇌ 2HI, the equilibrium concentrations are [H2] = 0.4 mol/L, [I2] = 0.12 mol/L, [HI] = 0.25 mol/L. Find the equilibrium constant Kc.

[H2] = 0.4[I2] = 0.12[HI] = 0.25
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 [H2].

[H₂]₀ = [I₂]₀ = 0.8 mol/LKc = 54
[H2] = 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 = 54. Find the equilibrium concentration [H2].

[H₂]₀ = [I₂]₀ = 0.1 mol/LKc = 54
[H2] = mol/L
5.Hard
PCl5​PCl3​Cl2​I0.200C−x+x+xE0.2 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.05 at the reaction temperature. A container starts with 0.2 mol/L of PCl₅ only. Find the equilibrium concentration [Cl2].

[PCl₅]₀ = 0.2 mol/LKc = 0.05
[Cl2] = mol/L
6.Hard
PCl5​PCl3​Cl2​I0.400C−x+x+xE0.4 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.01 at the reaction temperature. A container starts with 0.4 mol/L of PCl₅ only. Find the equilibrium concentration [Cl2].

[PCl₅]₀ = 0.4 mol/LKc = 0.01
[Cl2] = mol/L

Answer key

  1. 1. Kc = 0.08
  2. 2. Kc = 1.302
  3. 3. [H2] = 0.1712 mol/L
  4. 4. [H2] = 0.02139 mol/L
  5. 5. [Cl2] = 0.07808 mol/L
  6. 6. [Cl2] = 0.05844 mol/L

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