Reactivity Series S4

Reactivity SeriesReactions involving Metals

Chemical Properties• Forms CATIONS by the loss of electrons

• Form IONIC Compounds (eg. Metal Oxides/ Chlorides)

• Usually reacts with HCl / H2SO4 to give SALT

and H2(eg. M + HCL MCl + H20 / M + H2SO4 M2SO4 + H20)

• Reacts with O2 to form BASIC / AMPHOTERIC oxides

Reactivity and Periodic Table

Group, Reactivity (Cs is more reactive than Na)

Period, Reactivity (Ca is less reactive than K)

RXN with COLD WATER

•Metal + COLD Water Metal HYDORXIDE + H2

• Only the MORE REACTIVE metals react with COLD WATER

RXN with COLD WATER

Metal Observations

Equation

Potassium (K)

• Violent RXN• Heat produced

2K (s) + 2H20 (l ) 2KOH (aq) + H2 (g)

Sodium (Na)

• Violent RXN •Heat produced

2Na (s) + 2H20 (l ) 2NaOH (aq) + H2 (g)

Enough to ignite H2 (lilac flame)

H2 MAY be ignited (yellow flame)

RXN with COLD WATER (cont’d)

Metal Observations

Equation

Calcium (Ca)

• Reacts Readily• Heat produced

Ca (s) + 2H20 (l ) Ca(OH)2 (aq) + H2 (g)

Magnesium (Mg)

• Slow RXN• Heat produced

Mg (s) + 2H20 (l ) Mg(OH)2 (s) + H2 (g)

A test tube of H2 can be collected after a few days

If all RXN are exothermic, how do you determine which metal is more reactive than another?

RXN with COLD WATER (cont’d)

Metal Observations

Equation

Zinc (Zn)Iron (Fe)Lead (Pb)Copper (Cu)Silver (Ag)

NO RXN

NO RXN

Only the MORE REACTIVE metals are able to react with COLD WATER

RXN with STEAM•Metal + STEAM Metal OXIDE + H2

• The next few reactive metals are able to react with steam because of the high temperature

Think of how K, Na and Ca will react with steam?

Think of how Cs, Rb will react with cold water / steam?

RXN with STEAM Metal Observati

ons Equation

Magnesium (Mg)

• Violent RXN

Mg (s) + H20 (g) MgO (s) + H2 (g)

Zinc (Zn) • Reacts Readily

Zn (s) + H20 (g) ZnO (s) + H2 (g)

Iron (Fe) • Slow RXN

3Fe (s) + 4H20 (g) Fe304 (s) + 4H2 (g)

Pb, Cu, Ag

NO RXN NO RXN

RXN with DILUTE HCl/ H2SO4

•Metal + HCl Metal CHLORIDE + H2

2M (s) + 2HCl (aq) 2MCl (aq) + H2 (g)M (s) + 2HCl (aq) MCl2 (aq) + H2 (g)

•Metal + H2SO4 Metal SULPHATE + H2

• Only for Metals ABOVE Hydrogen in the Reactivity Series

RXN with Dilute HCl Metal Observati

ons Equation

Potassium (K)

• Violent RXN• Gas Burns

2K (s) + 2HCl (aq) 2KCl (aq) + H2 (g)

Sodium (Na)

• Violent RXN• Gas Burns

2Na (s) + 2HCl (aq) NaCl (aq) + H2 (g)

Calcium (Ca)

• Vigorous RXN• Effervescence

Ca (s) + 2HCl (aq) CaCl2 (aq) + H2 (g)

RXN with Dilute HCl (cont’d)

Metal Observations

Equation

Magnesium (Mg)

• Rapid RXN• Effervescence

Mg (s) + 2HCl (aq) MgCl2 (aq) + H2 (g)

Zinc (Zn) • Moderate RXN• Effervescence

Zn (s) + 2HCl (aq) ZnCl2 (aq) + H2 (g)

Iron (Fe) • Slow RXN• Effervescence

Fe (s) + 2HCl (aq) FeCl2 (aq) + H2 (g)

Cu, Ag, Au

NO RXN NO RXN

RXN with CONC. ACIDS

• Metals BELOW Hydrogen react with CONC ACIDS Able to oxidise metal to metal oxides firsteg. Cu (s) + HNO3 (l) Cu(NO3) 2 (aq) + 2NO2 + 2H2O (g)

What will happen to solid iron when reacted with HNO3?

Reactivity (as seen from experiments)

• K, Na, Ca are highly reactive metals• Mg, Zn, Fe are fairly reactive metals• Pb, Cu, Ag are unreactive metals

• Reactive metals tend to REACT to form

STABLE compounds

• Unreactive metals tend to REMAIN as metals Summary

HERE

Reactivity Series of Metals

• K, Na, Ca, Mg, Al, Zn, Fe,

Pb, H, Cu, Ag• IONS are STABLE• Metal HARD TO EXTRACT• Strong RA• Corrodes Easily

• ATOMS are STABLE• Metal EASY TO EXTRACT•Weaker RA• Does NOT Corrode Easily

Tendency for RXN to be Vigorous

Reactivity Series (Position of H)

• Metals placed ABOVE Hydrogen will displace the less reactive Hydrogen ions

from dilute acids or water RXN• Metals placed BELOW Hydrogen will

NOT displace Hydrogen ions NO RXN• Al does not react with dilute acids Al

reacts readily with Oxygen in air to form layer of

Reactivity Series (Position of Al)

• Al does NOT react readily with dilute acids Al reacts readily with Oxygen in air to form layer

of UNREACTIVE and INSOLUBLE Aluminium Oxide (Al2O3)

Oxide layer ADHERES strongly onto metal surface

Oxide PROTECTS reactive metal from reacting If oxide layer is removed by sandpaper, Al metal will react readily with the acids to produce the salt and H2 gas

Stability of Metal Compounds

• Reactive metals prefer to remain in IONIC FORM instead of elemental/ metallic form

• Compounds of metals high up in RS are

HIGHLY STABLE to heat / Not easily decomposed by heat

• Compounds of metals low down in RS are

LESS STABLE to heat / Easily decomposed by heat

Stability of Metal Oxides

• Oxides of metals ABOVE ZINC in RS

can be REDUCED to the metal via

ELECTROLYSIS of MOLTEN OXIDES(Na and K extracted by electrolysis of molten CHLORIDES)

• At the Cathode : Al3+ (l ) + 3e- Al (l) Mg2+ (l ) + 2e- Mg (l)

Stability of Metal Oxides

• Oxides of metals BELOW ZINC in RS can be

REDUCED to the metal via REDUCING AGENTS (eg. C, CO, H2)

• CuO (s) + C (s) Cu (s) + CO (g)Fe2O3 (s) + 3H2 (g) 2Fe (s) + H2O (g)

•ZINC OXIDE can be REDUCED ONLY

by CARBONZnO (s) + C (s) Zn (s) + CO (g)ZnO (s) + H2 (g) NO RXN

Stability of Metal Oxides

• Oxides of metals at the lowest of RS

easily REDUCED by HEATING alone 2AgO (s) 2Ag (s) + O2 (g)

Stability of Metal Hydroxides

• Hydroxides of metals BELOW CALCIUM decompose on heat to

their OXIDES to give STEAM Ca(OH)2 (s) CaO (s) + H2O (g)Cu(OH)2 (s) CuO (s) + H2O (g)

How to extract Calcium / Copper from their Hydroxides?

Stability of Metal Carbonates

• Carbonates of Sodium and Potassium are

STABLE TO HEATNa2CO3 (s) NO RXN

• Carbonates of metals BELOW CALCIUM decompose on heat to their

OXIDES to give CARBON DIOXIDECaCO3 (s) CaO (s) + CO2 (g)Fe2(CO3)3 (s) Fe2O3 (s) + 3CO2 (g)

Stability of Metal Nitrates

• Nitrates of SODIUM and

POTASSIUM decompose to

NITRITE and OXYGEN 2NaNO3 (s) 2NaNO2 (s) + O2 (g)2KNO3 (s) 2KNO2 (s) + O2 (g)

Stability of Metal Nitrates

• Nitrates BELOW SODIUM decompose to OXIDE, NITROGEN DIOXIDE and OXYGEN2Ca(NO3)2 (s) 2CaO (s) + 4NO2 (g) + O2 (g)4Al(NO3)3 (s) 2Al2O3 (s) + 12NO2 (g) + 3O2 (g)

• Nitrates BELOW COPPER decompose to the METAL, NITROGEN DIOXIDE and OXYGEN2AgNO3 (s) 2Ag (s) + 2NO2 (g) + O2 (g)

Summary HERE

Displacement Power of Metals

• A more reactive metal is capable of displacing a less reactive metal from its oxide/ aqueous solution of its saltMg (s) + CuO (s) MgO (s) + Cu (s)Mg (s) + Cu(OH)2 (aq) Mg(OH)2 (aq) + Cu (s)

• Movement of electrons! Mg (s) + Cu2+ (aq) Mg2+ (aq) + Cu (s)2e- : electrons flow

Recall: More reactive Metals tend to form IONS Less reactive Metals tend to form ATOMS