Topic 9.3 Reactivity

Assessment Statements Deduce a reactivity series based on the chemical behaviour of a group of oxidizing and reducing agents. (Examples include displacement reactions of metals and halogens. Standard electrode potentials will not be assessed) Deduce the feasibility of a redox reaction from a given reactivity series

References Moodle powerpoints Textbook (on moodle) Workbook exercises

Terms Activity Series Reactivity Displacement Reaction

Assessment statements Deduce a reactivity series based on the chemical behaviour of a group of oxidizing and reducing agents.

Demostration. Zinc reacts with a solution containing copper ions.

Demonstration Iron displaces copper from a solution of copper II sulphate Copper displaces silver from a solution of silver nitrate. Given this information deduce that the most reactive of the three metals

Magnesium reacts with zinc oxide: Mg + CuO MgO + Cu Sodium reacts with magnesium oxide: 2Na + MgO Na 2 O + Mg Zinc reacts with copper oxide: Zn + CuO ZnO + Cu Can you put these metals in order of reactivity?

Some substances are better oxidisers or reducers than others Reactivity series is derived experimentally CsCesium RbRubidium KPotassium NaSodium LiLithium SrStrontium CaCalcium MgMagnesium AlAluminum CCarbon ZnZinc CrChromium FeIron CdCadmium CoCobalt NiNickel SnTin PbLead HHydrogen BiBismuth CuCopper HgMercury AgSilver AuGold PtPlatinum

Activity series: ranks metals according to relative reactivity High reactivity Low (K Li Ba Ca Na Mg Al Zn Fe Ni Sn Pb (H)* Cu Hg Ag Au )

Displacement Reactions A common type of REDOX reaction is when a metal displaces another metal from its salt. Eg 2Na + CaCl 2  2NaCl + Ca ( the calcium is being displaced by the sodium) This will happen spontaneously.

Non-metals tend to be oxidants (gaining e-) Element lower in the table can oxidize the ion formed from an element higher in the table Cl 2 + 2I -  I 2 + 2Cl - Metals tend to lose electrons and are reductants Metal higher in the series will displace a metal lower on the series from its salts Metals above hydrogen are powerful enough reductants to reduce hydrogen ions to hydrogen Fe + Cu 2+  Cu + Fe 2+

Metal higher in the series will displace a metal lower on the series from its salts Metals above hydrogen are powerful enough reductants to reduce hydrogen ions to hydrogen Fe + Cu 2+  Cu + Fe 2+

Metals high in the series can displace hydrogen ions from cold water to form hydrogen gas and the metal hydroxide: E.g 2 M(s) + 2 H 2 O(l)  2 M + (aq) + H 2 (g) M represents K, Na or Li

Metals slightly lower in the series will displace hydrogen ions from steam to form hydrogen gas: Mg(s) + 2 H 2 O(g)  Mg(OH) 2 (s) + H 2 (g)

All metals above hydrogen in the reactivity series will displace hydrogen ions to form hydrogen gas and the metal salt: Zn(s) + 2 HCl(aq)  ZnCl 2 (aq) + H 2 (g)

The reactivity series gives info on which displacement reactions will occur spontaneously, but not on how fast they will occur. Lead in dilute sulfuric acid is very slow Concentration can be increased and warming can speed up the reaction

Aluminum, which is higher in the series, is slow to react initially. It has a coating to protect from aluminum oxide. This coating needs to wear off first, then the reaction is much faster

Ions of metals low in the series are good oxidizing agents, because they readily gain electrons. Silver (I) ions are a better oxidizing agent than copper (II) ions. The most reactive oxidizing agent is the species that gains the electrons most readily

You will be doing an experiment later to determine a reactivity series BUT for now lets predict a reactivity series based upon some experimental data…………….

Assessment Statement Deduce the feasibility of a redox reaction from a given reactivity series

Here you need to be able to predict whether a reaction will or will not occur given a reactivity series provided. Workbook Questions