Reaction kinetics worksheet with answers

Free printable Reaction kinetics 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
t (min)C (mol/L)5 minC = ?

A first-order reaction A → products has a rate constant of 0.15 min⁻¹. The initial concentration of A is 0.8 mol/L. Find the concentration CA after 5 min.

k = 0.15 min⁻¹CA0 = 0.8 mol/Lt = 5 min
CA = mol/L
2.Easy
t (min)C (mol/L)t½​ = ?C0​/2

A first-order reaction has a rate constant of 0.25 min⁻¹. Find its half-life t½.

k = 0.25 min⁻¹
t½ = min
3.Medium
t (min)C (mol/L)20 minC = ?

A reaction with rate law −rA = k·CA² has k = 0.4 L/(mol·min) and starts at 1 mol/L. Find the concentration CA after 20 min.

k = 0.4 L/(mol·min)CA0 = 1 mol/Lt = 20 min
CA = mol/L
4.Medium
t (min)X (%)t = ?50%

A first-order reaction in a batch reactor has k = 0.05 min⁻¹. How long does it take to reach 50% conversion? Find t.

k = 0.05 min⁻¹X = 50 %
t = min
5.Hard
Tk20 °Ck1​?3·k1​

A reaction has an activation energy of 75 kJ/mol. At 20 °C it is too slow. To what temperature T2 (in °C) must it be heated to make it 3 times faster?

Ea = 75 kJ/molT1 = 20 °Ck2/k1 = 3R = 8.314 J/(mol·K)
T2 = °C
6.Hard
Tk40 °C0.0550 °C0.0961

The rate constant of a reaction is 0.05 min⁻¹ at 40 °C and 0.0961 min⁻¹ at 50 °C. Find the activation energy Ea.

k1 = 0.05 min⁻¹T1 = 40 °Ck2 = 0.0961 min⁻¹T2 = 50 °CR = 8.314 J/(mol·K)
Ea = kJ/mol

Answer key

  1. 1. CA = 0.3779 mol/L
  2. 2. t½ = 2.773 min
  3. 3. CA = 0.1111 mol/L
  4. 4. t = 13.86 min
  5. 5. T2 = 30.85 °C
  6. 6. Ea = 54.97 kJ/mol

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