Catalysis of the reaction between zinc and sulfuric acid

Class practical

Zinc reacts with sulfuric acid to produce hydrogen. The reaction is catalysed by copper. The rate of reaction can be compared by means of the rate of production of hydrogen gas bubbles.
 

Lesson organisation

This is a quick and easy experiment that can be done individually or in pairs.

Health & Safety and Technical notes

Read our standard health & safety guidance

Dilute sulfuric acid, H₂SO₄(aq) (IRRITANT) - see CLEAPSS Hazcard, CLEAPSS Recipe Book and CLEAPSS L195 'Safer chemicals, safer reactions'. 

Copper(II) sulfate(VI) solution, CuSO₄(aq) - see CLEAPSS Hazcard and CLEAPSS Recipe Book. 

Procedure

a Put a few pieces of granulated zinc into each of the three test-tubes. Try to have approximately the same amount in each test-tube.

b Add 5 cm³ of dilute sulfuric acid to test-tube 1. Note the rate of production of gas bubbles.

c Add a few copper turnings to test-tube 2. Make sure they are in contact with the zinc. Add 5 cm³ of dilute sulfuric acid and note the rate of production of gas bubbles.

d Add 5 cm³ of dilute sulfuric acid to test-tube 3. Then add about 1 cm³ of the copper sulfate solution using a dropping pipette. Note the rate of production of gas bubbles. Note what happens to the colour of the copper sulfate solution. Note what happens to the surface of the pieces of zinc.

Teaching notes

If the granulated zinc pieces are shiny then the reaction in test-tube 1 is slow. The reaction may be faster if the zinc is not very pure. Bubbles of hydrogen form on the surface of the zinc. The reaction is:

Zinc + Sulfuric acid → Zinc sulfate + Hydrogen
Zn(s) + H₂SO₄(aq)→ ZnSO₄(aq)+ H₂(g)

In test-tube 2, copper is the catalyst for the reaction, and the reaction should be faster than in test-tube 1, but may not be as fast as test-tube 3.

In test-tube 3, zinc displaces copper from the copper sulfate solution and the surface of the zinc goes black. The displaced copper metal then acts as a catalyst for the reaction.

Zinc + Copper sulfate → Zinc sulfate + Copper
Zn(s) + CuSO₄ (aq) → ZnSO₄(aq)+ Cu(s)

There may be enough hydrogen produced in test-tube 3 for students to test for using a lighted splint.

Health and Safety checked October 2007 

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