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​0.5mol/L⇌2SO3​0.2mol/LKc​ = ?

For the reaction 2SO2 + O2 ⇌ 2SO3, the equilibrium concentrations are [SO2] = 0.3 mol/L, [O2] = 0.5 mol/L, [SO3] = 0.2 mol/L. Find the equilibrium constant Kc.

[SO2] = 0.3[O2] = 0.5[SO3] = 0.2
Kc =
2.Easy
2SO2​0.15mol/L+O2​0.3mol/L⇌2SO3​0.15mol/LKc​ = ?

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

[SO2] = 0.15[O2] = 0.3[SO3] = 0.15
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 = 9. Find the equilibrium concentration [H2].

[H₂]₀ = [I₂]₀ = 0.8 mol/LKc = 9
[H2] = mol/L
4.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 = 9. Find the equilibrium concentration [HI].

[H₂]₀ = [I₂]₀ = 0.5 mol/LKc = 9
[HI] = mol/L
5.Hard
PCl5​PCl3​Cl2​I0.400C−x+x+xE0.4 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.08 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 = 0.08
[PCl5] = mol/L
6.Hard
PCl5​PCl3​Cl2​I0.200C−x+x+xE0.2 − xxx

PCl₅ decomposes: PCl₅ ⇌ PCl₃ + Cl₂, with Kc = 0.02 at the reaction temperature. A container starts with 0.2 mol/L of PCl₅ only. Find the equilibrium concentration [PCl5].

[PCl₅]₀ = 0.2 mol/LKc = 0.02
[PCl5] = mol/L

Answer key

  1. 1. Kc = 0.8889
  2. 2. Kc = 3.333
  3. 3. [H2] = 0.32 mol/L
  4. 4. [HI] = 0.6 mol/L
  5. 5. [PCl5] = 0.2567 mol/L
  6. 6. [PCl5] = 0.146 mol/L

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