reactivity series s4
TRANSCRIPT
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