Reactions Of Metals and Metallic CompoundsThis is a featured page

Specific Objectives
Students should be able to:
1) describe the physical properties of metals
2) describe the chemical properties of metals( reactions with oxygen, water/ steam)
3) describe the reactions of metallic hydroxides and metallic oxides with dilute acids
4) describe the effect of heat on metallic hydroxides, carbonates and nitrates



Physical Properties of Metals
1) Usually solid at room temperature.
2) Have high melting points
3) Have high densities
4) Are good conductors of heat and electricity
5) Are usually lustrous
6) Some are ductile and malleable
7) Usually sonorous

The physical properties of metals are as a result of metallic structure













Figure 1. showing metallic structure


Metallic Bonding
Metals consist of cations surrounded by a 'sea' of mobile valence electrons. These mobile electrons are not associated with any one cation. The mobile electrons are attracted to to the cations. The force of attraction between the cations and the mobile electrons is called the METALLIC BOND.



Reason for the Physical Properties of Metals

1) High melting points - due to strong metallic bonds between cations and mobile electrons

2) High density - close packing of the cations

3) Good conductors of heat and electricity - due to the presence of mobile electrons that are able to carry an electric current and transfer heat by conduction

4) Shiny - due to light interacting with mobile electrons

5) Ductile and malleable- due to relative movement of cations without destroying metallic structure



Chemical Properties of Metals

1)
Reaction with oxygen
-

(a) Group I metals (alkali metals) react explosively with oxygen. For this reason, group I metals MUST be stored in liquid paraffin to prevent the reaction with oxygen.

eg. Reaction of Sodium with oxygen





The chemical equation representing the chemical reaction is as follows:

Na + O2 = Na2O

(b) Group II metals ( alkaline-earth metals) are easily tarnished by exposure to the air. Group II metals are less reactive with oxygen than

group I metals.

eg. Reaction with magnesium and oxygen





The chemical reaction may be represented as follows:

eg. Mg + O2 = MgO


(c) Other metals are oxidized by oxygen in the air. In these reactions, OXIDES ( basic or amphoteric) are formed.

Eg. 2Cu + O2 = 2CuO
(basic oxide)


2Al + 3O2 = 2Al2O3
(amphoteric oxide)


2) Reaction of Metals with Water / Steam

(a) Group I metals react violently with cold water to produce a metallic hydroxide and hydrogen






Eg. Potassium + Water = Potassium Hydroxide + Hydrogen

2K + 2H2O = 2KOH + H2


(b)( i) The more reactive group II metals react readily with cold water to produce a metallic hydroxide and hydrogen

Eg. Calcium + Oxygen = Calcium hydroxide + Hydrogen


Ca + 2H2O = Ca(OH)2 + H2

(ii) Magnesium reacts SLOWLY with cold water but READILY REACTS with steam to produce magnesium hydroxide and hydrogen.

Eg. Mg + 2H2O = Mg(OH)2 + H2



(c) Some other metals only react with steam when heated
.


3) Action of Metals with Dilute Hydrochloric Acid and Dilute Sulphuric Acid

Metals above hydrogen in the Reactivity Series will react with the above-mentioned acids to produce salt and hydrogen gas.

ie. Metal + Dilute Acid = Salt + Hydrogen

4) Metals Are Good Reducing Agents

Metals give away their outer electrons during bonding. Metals are ELECTRON DONORS and for this reason are good reducing agents.


Reactions of Metallic Compounds With Metals

1) Reactions of Bases with Dilute Acids

Bases include metallic oxides and hydroxides.

Acid + Base = Salt + Water (Neutralization)

2) Reactions of Carbonates With Dilute Acids


Acid + Carbonate = Carbon dioxide + Water + Salt



Action of Heat on Metallic Hydroxides, Carbonates and Nitrates

1) Action of Heat on Metallic Hydroxides

Potassium hydroxide (KOH) and sodium hydroxide are not decomposed at the temperature of the bunsen flames. All other

hydroxides decompose to give their corresponding metallic oxides and water.

For example

(a) Mg(OH)2 = MgO + H2O


2) Action of Heat on Carbonates

Potassium carbonate (K2CO3) and sodium carbonate (Na2CO3) are NOT decomposed at the temperature of a bunsen flame.

Other metallic carbonates will decompose to form the corresponding metallic oxide and carbon dioxide.

Eg. CuCO3 = CuO + CO2




3) Action of Heat on Nitrates

(a) The nitrates of sodium (NaNO3) and potassium (KNO3) will decompose to form the corresponding nitrites and oxygen eg.

Eg. 2KNO3 = 2KNO2 + O2

(b) Nitrates of metals from Calcium to copper decompose to form their corresponding oxides , nitrogen gas (brown gas) and

oxygen gas.

Eg. 2Zn(NO3)2 = 2ZnO + 4NO2 + O2



Questions

CXC CSEC Past Paper Question 2008 Paper 2 question 5 (d)

1) Two metal nitrates, P and Q, are separately heated. P gives off a colourless gas which rekindles a glowing splint. Q gives off a brown gas.

(i) Which of the two metal nitrates, P or Q, possibly contains:
- Group I metal
- Group II metal?

(ii) Write a chemical equation to show the reaction taking place when Q is heated.


CXC CSEC Past Paper 2006 Paper 3 Question 1a (iii)

Write a chemical equation to show the differences in products obtained when sodium nitrate and calcium nitrate are heated. (4 marks)


CXC CSEC Past Paper 2005 Paper 2 Question 5(d)

A compound of Q (Q has a valency of two) suspected to be a nitrate, has also been detected on Mars. How would the effect of heat on this metal nitrate
of Q differ from that of sodium nitrate?
Illustrate your answer by means of suitable equations in the spaces below:

(i) Effect of heat on sodium nitrate:

(ii) Effect of heat on the nitrate of Q :

Total (4 marks)

Past Paper 2003 Question 2(c)

The way nitrates of metals, decompose depends on the position of the metals in the reactivity series.

With the use of balanced equations, illustrate this statement by the action of heat on NaNO3 and Cu(NO3)2 in the space below:

Heat on NaNO3:

Heat on Cu(NO3)2:

Total (4 marks)


Past Paper 2002 Question 1a (ii)

The supply of copper (II) oxide ran out. The teacher suggested that copper (II) oxide could be prepared by heating either copper (II) nitrate ( a deliquescent compound) or copper (II) carbonate (a fine powder).

(i) Which of these two compounds is more suitable for the preparation of copper oxide? Give One reason for your choice.

(ii) Write balanced equations for the action of heat on (a) copper (II) nitrate and (b) copper (II) carbonate.

(Deliquescent means the compound absorbs moisture from the atmosphere and dissolves in it )


CXC CSEC Past Paper 2001 Question 5a and 5c

When lead (II) nitrate is strongly heated, it decomposes to give lead (II) oxide, nitrogen dioxide and oxygen.

a (i)Write a balanced equation for the action of heat on lead nitrate ( 2 marks)

(ii) How would you know that nitrogen dioxide is given off in the reaction? (2 marks)

(c) How do the products obtained upon heating lead nitrate differ fro those obtained upon heating sodium nitrate? (2 marks)




CXC CSEC Past Paper 1999 Question 2a (ii)

Write an equation to show the action of heat on sodium nitrate.






























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