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/C₀t½​ = 5 min0.5

A first-order reaction has a half-life of 5 min. Find its rate constant k.

t½ = 5 min
k = min⁻¹
2.Easy
t (min)C/C₀ (%)15 min?

A first-order reaction has a half-life of 30 min. What percentage f of the reactant is still left after 15 min?

t½ = 30 mint = 15 min
f = %
3.Medium
t (min)C (mol/L)5 minC = ?

A reaction with rate law −rA = k·CA² has k = 0.25 L/(mol·min) and starts at 0.5 mol/L. Find the concentration CA after 5 min.

k = 0.25 L/(mol·min)CA0 = 0.5 mol/Lt = 5 min
CA = mol/L
4.Medium
t (min)C (mol/L)5 min0.2

In a first-order reaction the concentration of A falls from 0.5 mol/L to 0.2 mol/L in 5 min. Find the rate constant k.

CA0 = 0.5 mol/LCA = 0.2 mol/Lt = 5 min
k = min⁻¹
5.Hard
Tk50 °Ck1​?2·k1​

A reaction has an activation energy of 70 kJ/mol. At 50 °C it is too slow. To what temperature T2 (in °C) must it be heated to make it 2 times faster?

Ea = 70 kJ/molT1 = 50 °Ck2/k1 = 2R = 8.314 J/(mol·K)
T2 = °C
6.Hard
Tk35 °C0.00275 °C0.0462

The rate constant of a reaction is 0.002 min⁻¹ at 35 °C and 0.0462 min⁻¹ at 75 °C. Find the activation energy Ea.

k1 = 0.002 min⁻¹T1 = 35 °Ck2 = 0.0462 min⁻¹T2 = 75 °CR = 8.314 J/(mol·K)
Ea = kJ/mol

Answer key

  1. 1. k = 0.1386 min⁻¹
  2. 2. f = 70.71 %
  3. 3. CA = 0.3077 mol/L
  4. 4. k = 0.1833 min⁻¹
  5. 5. T2 = 58.83 °C
  6. 6. Ea = 70.01 kJ/mol

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