Carbon Compound

Properties of Covalent compound

(a) Low melting points and boiling points

Because:

-          Molecules held by weak intermolecular forces.

-          Needs less energy to overcome these forces.

-         

(b) Cannot Conduct electricity

Because:

-          consists of neutral molecules.

-          Do not have ions that can move freely.

(c) does not dissolve in water

(d) dissolve in organic solvents.

Properties of Ionic compound

(a) High melting points and boiling points.

Because:

-          Ions held by strong electrostatic forces.

-          Needs a lot of energy to overcome these forces.

(b) Conduct electricity when in molten or aqueous solution.

Because:

-          In solid, ions are fixed in positions and do not move freely.

-          In molten state or aqueous solution, the ions can move freely.

(c) dissolve in water

(d) does not dissolve in organic solvents.

Covalent Bond (non-metal + non-metal) Sharing of electron

[proton number: C:6, O:8]

- Electron arrangement of atom C is 2.4

- Atom C needs 4 more electron to achieve stable octet electron arrangement.

- Atom C contributes 4 electron for sharing

- Electron arrangement of atom O is 2.6

- Atom O needs 2 more electron to achieve stable octet electron arrangement

- Atom O contributes 2 electron for sharing.

- covalent compound, CO₂ is formed

Ionic Bond (metal + non metal) Transfer of electron

[number of proton: Mg: 12, O: 8]

- Electron arrangement of magnesium atom is 2.8.2

- Magnesium atom donates 2 electron to achieve stable octet electron arrangement.

  Mg → Mg²⁺ + 2e

- Electron arrangement of oxygen atom is 2.6

- Oxygen atom receives 2 electron to achieve stable octet electron arrangement.

   O + 2e → O^2-

- Mg²⁺ ion and O^2‑ ion attract by strong electrostatic force to form ionic bond.

- Ionic compound, MgO is formed.

Period+Transition element

Quiz:

Answer:



Group 17

Quiz:

Answer:

Group 1

Quiz:

Answer:

Heat of combustion (calculation)

An experiment was carried out to determine the heat of combustion of ethanol.

The table below shows the experimental results

Volume of water in copper tin (cm3)	200
Mass of spirit lamp before heating (g)	189.55
Mass of spirit lamp after heating (g)	188.80
Initial temperature of water (C)	28.5
Maximum temperature of water (C)	53.5

a) Calculate the number of mole of ethanol used.

b) Calculate the heat absorbed by the water.

c) Calculate the heat of combustion of ethanol.

[Specific heat capacity of solution : 4.2 J g^{-1 0}C^-1 . Density of solution : 1 g cm^-3 ] 

Relative atomic mass: H = 1; C = 12; O = 16]

Answer: a) 0.0163 mol  b) 21 kJ           c) – 1288.34 kJ mol^-1