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
2SO2​0.3mol/L+O2​0.15mol/L⇌2SO3​0.3mol/LKc​ = ?

For the reaction 2SO2 + O2 ⇌ 2SO3, the equilibrium concentrations are [SO2] = 0.3 mol/L, [O2] = 0.15 mol/L, [SO3] = 0.3 mol/L. Find the equilibrium constant Kc.

[SO2] = 0.3[O2] = 0.15[SO3] = 0.3
Kc =
2.Easy
PCl5​0.1mol/L⇌PCl3​0.5mol/L+Cl2​0.5mol/LKc​ = ?

For the reaction PCl5 ⇌ PCl3 + Cl2, the equilibrium concentrations are [PCl5] = 0.1 mol/L, [PCl3] = 0.5 mol/L, [Cl2] = 0.5 mol/L. Find the equilibrium constant Kc.

[PCl5] = 0.1[PCl3] = 0.5[Cl2] = 0.5
Kc =
3.Medium
H2​I2​HII0.50.50C−x−x+2xE0.5 − x0.5 − x2x

0.5 mol/L of H₂ and 0.5 mol/L of I₂ are put in a container and react: H₂ + I₂ ⇌ 2HI, with Kc = 36. Find the equilibrium concentration [H2].

[H₂]₀ = [I₂]₀ = 0.5 mol/LKc = 36
[H2] = mol/L
4.Medium
H2​I2​HII0.20.20C−x−x+2xE0.2 − x0.2 − x2x

0.2 mol/L of H₂ and 0.2 mol/L of I₂ are put in a container and react: H₂ + I₂ ⇌ 2HI, with Kc = 36. Find the equilibrium concentration [H2].

[H₂]₀ = [I₂]₀ = 0.2 mol/LKc = 36
[H2] = mol/L
5.Hard
PCl5​PCl3​Cl2​I0.2500C−x+x+xE0.25 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.04 at the reaction temperature. A container starts with 0.25 mol/L of PCl₅ only. Find the equilibrium concentration [Cl2].

[PCl₅]₀ = 0.25 mol/LKc = 0.04
[Cl2] = mol/L
6.Hard
PCl5​PCl3​Cl2​I0.400C−x+x+xE0.4 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.5 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 = 0.5
[Cl2] = mol/L

Answer key

  1. 1. Kc = 6.667
  2. 2. Kc = 2.5
  3. 3. [H2] = 0.125 mol/L
  4. 4. [H2] = 0.05 mol/L
  5. 5. [Cl2] = 0.08198 mol/L
  6. 6. [Cl2] = 0.2623 mol/L

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