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​0.05mol/L+O2​0.1mol/L⇌2SO3​0.12mol/LKc​ = ?

For the reaction 2SO2 + O2 ⇌ 2SO3, the equilibrium concentrations are [SO2] = 0.05 mol/L, [O2] = 0.1 mol/L, [SO3] = 0.12 mol/L. Find the equilibrium constant Kc.

[SO2] = 0.05[O2] = 0.1[SO3] = 0.12
Kc =
2.Easy
PCl5​0.15mol/L⇌PCl3​0.1mol/L+Cl2​0.2mol/LKc​ = ?

For the reaction PCl5 ⇌ PCl3 + Cl2, the equilibrium concentrations are [PCl5] = 0.15 mol/L, [PCl3] = 0.1 mol/L, [Cl2] = 0.2 mol/L. Find the equilibrium constant Kc.

[PCl5] = 0.15[PCl3] = 0.1[Cl2] = 0.2
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 = 4. Find the equilibrium concentration [HI].

[H₂]₀ = [I₂]₀ = 0.5 mol/LKc = 4
[HI] = 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 = 16. Find the equilibrium concentration [H2].

[H₂]₀ = [I₂]₀ = 0.2 mol/LKc = 16
[H2] = mol/L
5.Hard
PCl5​PCl3​Cl2​I100C−x+x+xE1 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.02 at the reaction temperature. A container starts with 1 mol/L of PCl₅ only. Find the equilibrium concentration [PCl5].

[PCl₅]₀ = 1 mol/LKc = 0.02
[PCl5] = mol/L
6.Hard
PCl5​PCl3​Cl2​I0.800C−x+x+xE0.8 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.04 at the reaction temperature. A container starts with 0.8 mol/L of PCl₅ only. Find the equilibrium concentration [PCl5].

[PCl₅]₀ = 0.8 mol/LKc = 0.04
[PCl5] = mol/L

Answer key

  1. 1. Kc = 57.6
  2. 2. Kc = 0.1333
  3. 3. [HI] = 0.5 mol/L
  4. 4. [H2] = 0.06667 mol/L
  5. 5. [PCl5] = 0.8682 mol/L
  6. 6. [PCl5] = 0.64 mol/L

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