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SS3: CHEMISTRY - 2ND TERM

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  1. Quality of Petrol (Octane Number)| Week 1
    1 Topic
    |
    1 Quiz
  2. Natural Gas | Week 2
    3 Topics
    |
    1 Quiz
  3. Introduction to Metals | Week 3
    3 Topics
    |
    1 Quiz
  4. The Alkali Metals | Week 4
    4 Topics
    |
    1 Quiz
  5. Alkaline Earth Metals | Week 5
    4 Topics
    |
    1 Quiz
  6. Aluminium & Tin | Week 6
    3 Topics
    |
    1 Quiz
  7. Transition Metals of the First Series | Week 7
    4 Topics
    |
    1 Quiz
  8. Ethical, Legal & Social Issues | Week 8
    3 Topics
    |
    1 Quiz
  9. Fats & Oils - Soaps & Detergents | Week 9
    4 Topics
  10. Giant Molecules | Week 10
    6 Topics



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calcium

Physical Properties of Calcium:

AppearanceSilvery grey solid.
Relative density1.55g/cm3.
Boiling point1484°C.
Melting point837-841 °C.
HardnessRelatively soft metal.
DuctilityIt is ductile.
It can be beaten into extremely thin sheets.
It can be pressed, rolled, and cut.
MalleabilityIt is malleable.
Capable of being shaped or bent.
ConductivityGood conductor of heat and electricity.
Crystalline structureCubic.
Tensile StrengthRelatively low tensile strength.

Chemical Properties of Calcium:

Reaction of Calcium with Water:

Calcium reacts with cold water slowly and rapidly with warm water to form Calcium hydroxide, Ca(OH)2 and Hydrogen gas.

Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

After the reaction is complete we observe that the metal floats in water because of the hydrogen gas which sticks to the surface of the metal.

Reaction of Calcium with Air:

On exposure to air, Calcium reacts slowly with oxygen, water vapour, and nitrogen of the air and loses its metallic lustre, due to the formation of a white film of quick lime or calcium oxide on the metal surface.

When calcium is heated in air, it burns with a brick red flame to form a mixture of white calcium oxide, CaO, and calcium nitride, Ca3N2

2Ca(s) + O2(g) → 2CaO(s)

3Ca(s) + N2(g) → Ca3N2(s)

In the presence of atmospheric moisture and CO2, some calcium hydroxide and calcium trioxocarbonate(IV)may also be formed.

CaO(s) + H2O(l)→ Ca(OH)2(g)

Ca(OH)2(g) + CO2(g) → CaCO3(s) + H2O(l)

Reaction of Calcium with Acids:

Calcium metal dissolves readily in dilute or concentrated hydrochloric acid forming solutions containing Ca(II) ions along with hydrogen gas, H2.

Ca(s) + 2 HCl(aq)→ Ca2+(aq) + 2 Cl(aq) + H2(g)

Reaction of Calcium with Halogens:

Calcium reacts readily with the halogens fluorine, F2, chlorine, Cl2 bromine, Br2, or iodine, I2, and burns to form corresponding dihalides, calcium(II) fluoride, CaF2 , calcium(II) chloride, CaCl2, calcium(II) bromide, CaBr2, and calcium(II) iodide, CaI2.

The reactions with fluorine and chlorine are exothermic while the reactions with bromine and iodine require heat to enable the formation of the products.

Ca(s) + F2(g) → CaF2(s)

Ca(s) + Cl2(g) → CaCl2(s)

Ca(s) + Br2(g) → CaBr2(s)

Ca(s) + I2(g) → CaI2(s)

Reaction of Calcium with Non-Metals:

Calcium combines directly with nitrogen, chlorine, sulphur and hydrogen on heating.

3Ca(s) + N2(g) → Ca3N2(s) (Calcium nitride)

Ca(s) + Cl2(g) → CaCl2(s) (Calcium chloride)

Ca(s) + H2(g) → CaH2(s) (Calcium hydride)

Reaction of Calcium with Ammonia:

When ammonia is passed over heated calcium, the reaction is as follows;

3Ca(s) + 2NH3(g) → Ca3N2(s) + 3H2(g)

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