Activity Series (Reactivity Series) of Metals Chemistry Tutorial

Key Concepts

• An activity series is a list of substances in order from most reactive to least reactive.

• The relative reactivity of metals can be determined using a number of chemical reactions.

  The most commonly used reactions are reactions with:

  (a) water (in which hydrogen is displaced from water to produce hydrogen gas)

  (b) non-oxidizing acids such as dilute hydrochloric acid or dilute sulfuric acid (in which hydrogen is displaced from acid to produce hydrogen gas).

• A metal activity series places metals in order of relative reactivity, from most reactive to least reactive:

• In general:

1. Group 1 (alkali) metals and Group 2 (alkaline earth) metals are more active than transition metals.

   (Silver, platinum and gold are so unreactive that they are called noble metals (or inactive metals).

2. A more active metal loses electrons more easily than a less active metal.

   A more active metal is a stronger reductant than a less active metal.
       (A substance that loses electrons is called a reductant or reducing agent)

3. A more active element displaces a less active element in a chemical reaction.

   Enabling us to make predictions on the probable outcome of a chemical reaction!

4. The further apart two elements are in the activity series, the more energy the reaction produces.

   Enabling us to predict the relative amount of energy released during a chemical reaction!

5. If a reaction occurs, a more active metal will react more rapidly than a less active metal.

Summary

Hydrogen Displacement Reaction Examples

Question 1. A piece of clean magnesium is placed in a beaker with dilute hydrochloric acid.
Will a hydrogen gas be produced?

1. Determine the relative activity of magnesium and hydrogen using the activity series:
   magnesium is more active than hydrogen
2. Determine whether a reaction will occur:
   A metal that is more active than hydrogen will displace hydrogen from an acid.
   Magnesium (more active) will displace hydrogen (less active) from acidic solution.
   A reaction will occur.

   Yes, hydrogen gas will be produced.

Question 2. A piece of clean copper is placed in a beaker with dilute sulfuric acid.
Will a hydrogen gas be produced?

1. Determine the relative activity of copper and hydrogen using the activity series:
   copper is less active than hydrogen
2. Determine whether a reaction will occur:
   A metal that is more active than hydrogen will displace hydrogen from an acid.
   Copper is not more active than hydrogen so it will not displace hydrogen from acidic solution.
   A reaction will not occur.

   No, hydrogen gas will not be produced.

Question 3. A student pours 100 mL of 0.1 mol L^-1 hydrochloric acid into each of two 250 mL beakers labelled A and B.
A thermometer is suspended in each beaker, and the initial temperature of each acidic solution recorded.
To beaker A the student adds a clean piece of iron.
To beaker B the student the adds the same amount of clean zinc.
In which beaker, A or B, would you expect the greatest temperature increase in the first minute of the experiment?

1. Determine the relative activity of iron, zinc and hydrogen using the activity series:
   Zinc is more active than iron which is more active than hydrogen.
   zinc > iron > hydrogen
2. Determine whether a reaction will occur:
   A metal that is more active than hydrogen will displace hydrogen from an acid.
   Zinc is more active than hydrogen, a reaction will occur (bubbles of hydrogen gas form).
   Iron is more active than hydrogen, a reaction will occur (bubbles of hydrogen gas form).
3. Determine the relative amount of energy released during the reactions:
   The further apart the elements are in the activity series, the more energy is released.
   The distance between zinc and hydrogen in the activity series is greater than the distance between iron and hydrogen.
   The reaction between zinc and acid will release more energy than the reaction between iron and zinc.
4. Determine the relative temperature increases:
   Energy released as heat can be measured using a thermometer.
   More energy released will produce a greater temperature increase.
   The reaction between zinc and acid produces more energy so the temperature in this beaker will increase more.

   The greatest temperature increase will be recorded for beaker B.

Metal Displacement Reactions Examples

Question 1. A piece of clean zinc is placed in a solution containing copper ions.
Will zinc displace copper from the solution?

1. Determine the relative activity of each metal using the activity series:
   zinc is more active than copper
2. Determine whether a reaction will occur:
   a more active metal displaces a less active metal from solution
   Zinc (more active metal) will displace copper (less active metal) from solution.

   Yes, a reaction occurs.

Question 2. A clean piece of lead is placed in a solution containing sodium ions.
Will lead displace sodium from the solution?

1. Determine the relative activity of each metal using the activity series:
   sodium is more active than lead
2. Determine whether a reaction will occur:
   a more active metal displaces a less active metal from solution
   Sodium (more active metal) will displace lead (less active metal) from solution.

   No, a reaction will not occur. Lead will not displace sodium from the solution.

Question 3. Consider the following experimental set-up:
Beaker A : a clean piece of magnesium is placed in 0.5 mol L^-1 CuSO_(aq).
Beaker B : a clean piece of zinc is placed in 0.5 mol L^-1 CuSO_(aq).
Which beaker A or B will produce the greatest amount of energy?

1. Determine the relative activity of each metal using the activity series:
   magnesium is more active than zinc which is more active than copper
2. Determine whether a reaction will occur:
   a more active metal displaces a less active metal from solution
   Magnesium (more active metal) will displace copper (less active metal) from solution.
   Zinc (more active metal) will displace copper (less active metal) from solution.
3. Determine the relative amount of energy released in each reaction:
   the further apart two metals are in the activity series, the more rapidly react, the more energy is released.
   magnesium is further from copper in the activity series than zinc.
   The reaction between magnesium and copper ions will produce more energy than the reaction between zinc and copper ions.

   Beaker A produces more energy.

Reactions with Oxygen Gas Examples

Question 1. Clean sodium and clean zinc will both react with oxygen gas to form metal oxides.
Which metal is likely to react faster at room temperature and pressure?

1. Determine the relative activity of each metal using the activity series:.
   Sodium is more active than zinc.
2. Determine the relative rate of reaction:
   A more active metal is expected to react faster than a less active metal.
   Sodium is more active than zinc.

   Sodium will react faster than zinc.

Question 2. Under certain conditions, both copper and magnesium will react with oxygen gas to form oxides.
One of these reactions occurs slowly at room temperature, the other metal will not react with oxygen gas unless it is heated.
Which of the two metals will only react with oxygen gas if it is heated?

1. Determine the relative activity of each metal using the activity series:.
   Magnesium is more active than copper.
2. Determine the relative rate of reaction:
   A more active metal is expected to react faster than a less active metal.
   Magnesium is more active than copper.
   Magnesium will react faster than copper.
3. Determine which reaction is more likely to require heat:
   Heating a reaction mixture speeds up the rate of the reaction.
   Since magnesium is more active than copper it is more likley to be the reaction that occurs at room temperature and pressure.

   Copper, being less active than magnesium, is more likely to have the slower reaction rate and therefore is more likley to require heat to speed up the rate of reaction.