Question 3
- Explain each of the following observations:
(i) sodium metal conducts electricity both in the solid and molten states but sodium chloride only conducts electricity when molten;;
(ii) at room temperature, most covalent compounds are gases or liquids whereas ionic compound are solids. [8 marks] [6 marks] - Give the IUPAC name of each of the following compounds:
(i) CH3C(CH3)2OH;
(ii) C(CH3)4;
(iii) HCOOH. [3 marks] - Identify the functional group in each of the compounds:
(i) CH3CH2COOCH2CH3;
(ii) CH3CH(OH)CH3;
(iii) HCOOH. [3 marks] - When a given mass of CaCO3 was heated, 0.25 dm3 of a gas is collected at 250 C and at a pressure of 120 kNm-2.
(i) Write an equation for the reaction.
. (ii) Calculate the mass of the:
(I) gaseous product obtained;
(II) CaCO3 heated.
[C = 12.0, O = 16.0, Ca = 40.0, R = 8.314 Jk-1mol-1] [11 marks]
The expected answers include:
- (i) Sodium metal has delocalized / mobile electrons which moves in both solid and molten states whereas sodium chloride has fixed ions / cannot move / only vibrate in the solid state but mobile ions in the molten state.
(ii) Covalent compounds consist of molecules with weak attractive forces / intermolecular forces / van der Waal’s forces between them. Ionic compounds consist of positive and negative ions with strong attractive / electrostatic forces between ion.OR
In covalent compounds molecules are loosely held while in ionic compounds ions are strongly held - (i) 2 – methylpropan-2-ol / 2 – methyl -2- propanol
(ii) 2, 2-dimethylpropane
(iii) methylmethanoate - (i) alkanoate (ester) / -COOCH2CH3
(ii) alkanol / - OH
(iii) alkanoic acid / - COOH - (i) CaCO3(s) heat CaO(s) + CO2(g)
