(a) State the conditions necessary for the cracking of long-chain hydrocarbons to produce more gasoline.
(b) State two reasons why metallic objects are electroplated
(c) (i) Explain briefly why calcium oxide cannot be used to dry hydrogen chloride gas.
(ii) State one drying agent for hydrogen chloride gas.
(d) Concentrated trioxonitrate (V) acid was added to a solution of iron (II) tetraoxosulphate (VI) and the mixture heated. The mixture turned from pale green to yellow with the evolution of a brown gas. Explain briefly these observations.
(e) (i) Write the equation for the reaction between zinc oxide and
- dilute tetraoxosulphate (VI) acid,
- sodium hydroxide solution.
(ii) State which property of zinc oxide is shown by the reaction in (e)(i).
(f) Two isotopes of chlorine are \(^{35}_{17}\)Cl and \(^{37}_{17}\)Cl State one:
- similarity;
- difference between the isotopes.
(g) State the two products formed when chlorine water is exposed to sunlight.
(h) Consider the reaction represented by the following equation:
State the:
- species that is undergoing oxidation;
- oxidizing agent.
(i) What is meant by carbon-12 scale?
(j) State two properties of a chemical system in equilibrium.
(a) The cracking of long-chain hydrocarbons to produce more gasoline requires the following conditions:
- High temperature, typically between 500 and 900 °C.
- Presence of a catalyst, such as silica or alumina.
- High pressure, usually around 1 atmosphere or higher.
(b) Metallic objects are electroplated for two main reasons:
- To improve their appearance or to provide a decorative finish.
- To protect them from corrosion or wear and tear.
(c)
- (i) Calcium oxide cannot be used to dry hydrogen chloride gas because it reacts with it to form calcium chloride, which is a hygroscopic compound and will not remove water vapor from the gas.
- (ii) Phosphorus pentoxide (P2O5) can be used as a drying agent for hydrogen chloride gas.
(d) The pale green color of the iron (II) tetraoxosulphate (VI) solution indicates the presence of Fe2+ ions. Upon adding concentrated trioxonitrate (V) acid and heating, the Fe2+ ions are oxidized to Fe3+ ions, which give the yellow color to the solution. The brown gas evolved is likely to be nitrogen dioxide (NO2), which is a product of the reaction between the trioxonitrate (V) acid and the Fe2+ ions.
(e)
- (i) The equation for the reaction between zinc oxide and dilute tetraoxosulphate (VI) acid is:
ZnO + H2SO4 → ZnSO4 + H2O
- (ii) The property of zinc oxide shown by the reaction is its basic nature, as it reacts with an acid to form a salt and water.
(f) Similarity: Both isotopes of chlorine have the same number of electrons and protons, and hence have the same chemical properties.
Difference: The isotopes have different atomic masses due to the presence of different numbers of neutrons in their nuclei.
(g) When chlorine water is exposed to sunlight, the two products formed are:
- Chlorine free radicals (Cl*) which are highly reactive and can participate in further reactions.
- Oxygen gas (O2) which is a byproduct of the reaction between the Cl* radicals and water molecules.
(h) The reaction can be represented as follows:
Cr2O72- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O
Species undergoing oxidation: Fe2+ ions
Oxidizing agent: Cr2O72- ions
(i) The carbon-12 scale is a standard used to define the relative atomic masses of elements. It is based on the isotope carbon-12
(a) The cracking of long-chain hydrocarbons to produce more gasoline requires the following conditions:
- High temperature, typically between 500 and 900 °C.
- Presence of a catalyst, such as silica or alumina.
- High pressure, usually around 1 atmosphere or higher.
(b) Metallic objects are electroplated for two main reasons:
- To improve their appearance or to provide a decorative finish.
- To protect them from corrosion or wear and tear.
(c)
- (i) Calcium oxide cannot be used to dry hydrogen chloride gas because it reacts with it to form calcium chloride, which is a hygroscopic compound and will not remove water vapor from the gas.
- (ii) Phosphorus pentoxide (P2O5) can be used as a drying agent for hydrogen chloride gas.
(d) The pale green color of the iron (II) tetraoxosulphate (VI) solution indicates the presence of Fe2+ ions. Upon adding concentrated trioxonitrate (V) acid and heating, the Fe2+ ions are oxidized to Fe3+ ions, which give the yellow color to the solution. The brown gas evolved is likely to be nitrogen dioxide (NO2), which is a product of the reaction between the trioxonitrate (V) acid and the Fe2+ ions.
(e)
- (i) The equation for the reaction between zinc oxide and dilute tetraoxosulphate (VI) acid is:
ZnO + H2SO4 → ZnSO4 + H2O
- (ii) The property of zinc oxide shown by the reaction is its basic nature, as it reacts with an acid to form a salt and water.
(f) Similarity: Both isotopes of chlorine have the same number of electrons and protons, and hence have the same chemical properties.
Difference: The isotopes have different atomic masses due to the presence of different numbers of neutrons in their nuclei.
(g) When chlorine water is exposed to sunlight, the two products formed are:
- Chlorine free radicals (Cl*) which are highly reactive and can participate in further reactions.
- Oxygen gas (O2) which is a byproduct of the reaction between the Cl* radicals and water molecules.
(h) The reaction can be represented as follows:
Cr2O72- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O
Species undergoing oxidation: Fe2+ ions
Oxidizing agent: Cr2O72- ions
(i) The carbon-12 scale is a standard used to define the relative atomic masses of elements. It is based on the isotope carbon-12