Section 8.3 Activity Series of the Elements

Objectives Explain the significance of an activity series. Use an activity series to predict whether a given reaction will occur and what the products will be.

Activity The ability of an element to react. The greater the ability, the greater the activity.

Activity Series A list of elements organized according to the ease with which the elements undergo certain chemical reactions.

The Order Is usually determined by single-replacement reactions. The most active element is placed at the top of the series and can replace any element below it. An element further down can replace any element below it but not any above it.

See Table 8-3 on p. 266 The fact that a chemical equation can be written does not mean that it will happen. Activity series are used to help predict whether certain chemical reactions will occur.

An Activity Series is Based on Experiment They are used as a general guide for assessing relative reactivities of substances and for predicting reaction outcomes.

Example From the table, aluminum is higher than zinc, and cobalt is below sodium. So: 2Al(s) + 3ZnCl2(aq) → 3Zn(s) + 2AlCl3(aq) does occur, but Co(s) + 2NaCl(aq) → no reaction

Example #1 Zn(s) + H2O(l) → no reaction Zinc reacts with water only when it is in the gas phase as steam.

Example #2 Sn(s) + O2(g) → SnO2(s) Any metal more reactive than silver will form an oxide. Tin is above silver, so the oxide is formed.

Example #3 Cd(s) + Pb(NO3)2(aq) → Pb(s) + Cd(NO3)2(aq) Cadmium is above lead in the series, so the reaction does occur.

Example #4 Cu(s) + HCl(aq) → no reaction Any metal more active than hydrogen will replace it in an acid, but copper is below hydrogen in the series.