(a) State the role of each of the following substances in the treatment of river water for town supply (i) Sand bed. (ii) Alum (iii) Chlorine
(b)(i) Give three major uses of H\(_2\)SO\(_4\)
(ii) Explain the following observation: A strip of blue litmus paper dropped into concentrated H\(_2\)SO\(_4\) becomes charred whereas in dilute H\(_2\)SO\(_4\), it turns red and is not charred.
(iii) Write an equation to show how concentrated H\(_2\)SO\(_4\) reacts with zinc.
(c)(i) List two gaseous pollutants that can be generated by burning coal.
(ii) Explain why coal burns more easily when it is broken into pieces than when it is in lump form.
(ii) What gas is responsible for most of the explosions in coal mines?
(iv) Name: the non-volatile residue left behind after the destructive distlillation of coal
(d)(i) What is meant by allotropy?
(ii) Name two crystalline allotropes of carbon
(iii) Name two elements apart from carbon, which exhibit allotropy
(iv) It is now known that carbon has an allotropic form called fullerene, containing molecules of formula C\(_{60}\). Calculate the mass of one mole of these molecules [C = 12]
(a) In the treatment of river water for town supply:
(i) Sand bed: used for filtration to remove suspended solid particles.
(ii) Alum: used as a coagulant to cause fine suspended and colloidal particles to clump together and settle.
(iii) Chlorine: used for sterilization; it kills harmful bacteria and other micro-organisms.
(b)(i) Three major uses of H2SO4:
- Manufacture of fertilizers.
- As an electrolyte in lead-acid batteries.
- Manufacture of detergents, pigments and plastics.
(ii) Concentrated H2SO4 is a strong dehydrating agent. It removes water from the blue litmus paper, leaving carbon behind; hence, the paper becomes black and charred. Dilute H2SO4 produces H3O+ ions in water, which turn blue litmus red. It does not char the paper because it is not sufficiently dehydrating.
(iii)
Zn + 2H2SO4(conc.) → ZnSO4 + SO2 + 2H2O
(c)(i) Two gaseous pollutants generated by burning coal are sulphur(IV) oxide, SO2, and carbon(II) oxide, CO.
(ii) When coal is broken into smaller pieces, it has a larger surface area exposed to oxygen in the air. This increases the rate of combustion, so it burns more easily than coal in lump form.
(iii) Methane, CH4 (firedamp), is responsible for most explosions in coal mines.
(iv) The non-volatile residue left after the destructive distillation of coal is coke.
(d)(i) Allotropy is the existence of an element in two or more different forms in the same physical state.
(ii) The two crystalline allotropes of carbon are diamond and graphite.
(iii) Two elements apart from carbon that exhibit allotropy are sulphur and phosphorus.
(iv)
Mass of one mole of C60 = 60 × 12 g = 720 g mol−1.
(a) In the treatment of river water for town supply:
(i) Sand bed: used for filtration to remove suspended solid particles.
(ii) Alum: used as a coagulant to cause fine suspended and colloidal particles to clump together and settle.
(iii) Chlorine: used for sterilization; it kills harmful bacteria and other micro-organisms.
(b)(i) Three major uses of H2SO4:
- Manufacture of fertilizers.
- As an electrolyte in lead-acid batteries.
- Manufacture of detergents, pigments and plastics.
(ii) Concentrated H2SO4 is a strong dehydrating agent. It removes water from the blue litmus paper, leaving carbon behind; hence, the paper becomes black and charred. Dilute H2SO4 produces H3O+ ions in water, which turn blue litmus red. It does not char the paper because it is not sufficiently dehydrating.
(iii)
Zn + 2H2SO4(conc.) → ZnSO4 + SO2 + 2H2O
(c)(i) Two gaseous pollutants generated by burning coal are sulphur(IV) oxide, SO2, and carbon(II) oxide, CO.
(ii) When coal is broken into smaller pieces, it has a larger surface area exposed to oxygen in the air. This increases the rate of combustion, so it burns more easily than coal in lump form.
(iii) Methane, CH4 (firedamp), is responsible for most explosions in coal mines.
(iv) The non-volatile residue left after the destructive distillation of coal is coke.
(d)(i) Allotropy is the existence of an element in two or more different forms in the same physical state.
(ii) The two crystalline allotropes of carbon are diamond and graphite.
(iii) Two elements apart from carbon that exhibit allotropy are sulphur and phosphorus.
(iv)
Mass of one mole of C60 = 60 × 12 g = 720 g mol−1.
