Practical: Effect of Catalysts on Rate of Reaction

Purpose of experiment

Investigate how catalysts change the rate of reaction

Typical reaction

Decomposition of hydrogen peroxide

Catalyst used

Manganese(IV) oxide (MnO₂)

Reaction observed

Hydrogen peroxide → water + oxygen

Evidence of reaction

Oxygen gas produced

Measurement method

Use gas syringe to measure volume of O₂ over time

Alternative method

Use mass loss as O₂ escapes

Prediction

Catalyst increases rate but does not change total gas produced

Collision theory link

Catalyst lowers activation energy → more successful collisions

Independent variable

Presence or absence of catalyst

Dependent variable

Rate of oxygen production

Control variables

Volume of H₂O₂, concentration, temperature, mass of catalyst

Graph result

Catalyst curve is steeper but reaches same final volume

Reason same final volume

Catalyst does not change amount of reactants or products

Sources of error

Gas leaks, inconsistent catalyst mass, inaccurate timing

Improving accuracy

Use airtight apparatus, digital timer, constant catalyst mass

Key idea

Catalysts speed up reactions by lowering activation energy, not by changing yield