(i) Name two amorphous forms of carbon (ii) State the reason why graphite is a lubricant but diamond is not. (iii) Draw and label a diagram for the laborato...
(ii) State the reason why graphite is a lubricant but diamond is not.
(iii) Draw and label a diagram for the laboratory preparation of a dry sample of carbon (IV) oxide.
(b)(i) Give one example of the following: I. Soil pollutant; II. Water pollutant; III. Air pollutant.
(ii) State the major use of sulphur (IV) oxide in a chemical industry.
(c)(i) Explain in terms of the kinetic theory why petrol is volatile
(ii) State two criteria for determining the purity of a substance.
(iii) Mention one use of each of the following gases: I. Krypton; II. Argon
(d)(i) When zinc metal was added to aqueous copper (I) tetraoxosulphate (VI), the solution turned colourless. I. Name the compound in the colourless solution. II. Write the ionic equation for the reaction. Ill. State what would be observed when a few drops of sodium hydroxide solution is added to a portion of the colourless solution.
(ii) Calculate the volume of CO\(_2\) produced when 5.3g of Na\(_2\)CO\(_3\) reacted with excess HNO\(_{3(aq)}\) + Na\(_2\)CO\(_3\) + 2HNO\(_{3(aq)}\) \(\to\) 2NaNO\(_{3(aq)}\) + CO\(_{2(g)}\) + H\(_2\)O\(_{(l)}\) [H = 1, C = 12, N = 14, O = 16, Na = 23, 1 mole of a gas occupies 22.4 dm\(^3\) at s.t.p.]
(a)(i) Two amorphous forms of carbon: wood charcoal and soot (lamp-black). (Coke and carbon black are also acceptable.)
(ii) Why graphite is a lubricant but diamond is not: in graphite the carbon atoms are arranged in flat parallel layers held together by weak forces, so the layers slide easily over one another, giving graphite its slippery, lubricating property. In diamond every carbon atom is joined to four others by strong covalent bonds in a rigid three-dimensional lattice with no layers to slide, so diamond is hard and cannot act as a lubricant.
(iii) Laboratory preparation of a dry sample of carbon(IV) oxide: marble chips (calcium trioxocarbonate(IV)) are placed in a flask and dilute hydrochloric acid is run onto them through a thistle funnel whose stem dips below the acid. The carbon(IV) oxide evolved is passed first through water to remove any hydrogen chloride gas, then through concentrated tetraoxosulphate(VI) acid to dry it, and the dry gas is finally collected in a gas jar by upward delivery (downward displacement of air), since carbon(IV) oxide is denser than air.
Laboratory preparation of a dry sample of carbon(IV) oxide: marble chips and dilute HCl in the flask, the gas washed through water, dried over concentrated H₂SO₄, and collected by upward delivery in a gas jar.
(b)(i) I. Soil pollutant: pesticides (or excess fertilizers, polythene, oil spillage). II. Water pollutant: sewage/domestic waste (or factory effluent, crude oil). III. Air pollutant: sulphur(IV) oxide (or carbon(II) oxide, oxides of nitrogen, chlorofluorocarbons).
(ii) The major industrial use of sulphur(IV) oxide is in the manufacture of tetraoxosulphate(VI) acid, \( \text{H}_2\text{SO}_4 \), by the Contact process.
(c)(i) The molecules of petrol are held together by only very weak intermolecular forces of attraction. At room temperature the molecules already possess enough kinetic energy to overcome these weak forces, so they escape readily from the liquid surface into the vapour state; hence petrol is volatile.
(ii) Two criteria for purity: a pure substance has a sharp, constant melting point and a fixed, constant boiling point. (A fixed density or refractive index is also acceptable.)
(iii) I. Krypton: used in photographic flash lamps and fluorescent (fluorescent tube) lighting. II. Argon: used to provide an inert atmosphere in gas-filled electric light bulbs and in welding.
(d)(i) I. The colourless solution contains zinc tetraoxosulphate(VI), ZnSO₄.
II. Ionic equation: \( \text{Zn}_{(s)} + \text{Cu}^{2+}_{(aq)} \rightarrow \text{Zn}^{2+}_{(aq)} + \text{Cu}_{(s)} \).
III. On adding a few drops of sodium hydroxide solution, a white gelatinous precipitate of zinc hydroxide, \( \text{Zn(OH)}_2 \), is formed (which redissolves in excess sodium hydroxide).
(d)(ii) Volume of CO₂ produced from 5.3 g of Na₂CO₃:
(a)(i) Two amorphous forms of carbon: wood charcoal and soot (lamp-black). (Coke and carbon black are also acceptable.)
(ii) Why graphite is a lubricant but diamond is not: in graphite the carbon atoms are arranged in flat parallel layers held together by weak forces, so the layers slide easily over one another, giving graphite its slippery, lubricating property. In diamond every carbon atom is joined to four others by strong covalent bonds in a rigid three-dimensional lattice with no layers to slide, so diamond is hard and cannot act as a lubricant.
(iii) Laboratory preparation of a dry sample of carbon(IV) oxide: marble chips (calcium trioxocarbonate(IV)) are placed in a flask and dilute hydrochloric acid is run onto them through a thistle funnel whose stem dips below the acid. The carbon(IV) oxide evolved is passed first through water to remove any hydrogen chloride gas, then through concentrated tetraoxosulphate(VI) acid to dry it, and the dry gas is finally collected in a gas jar by upward delivery (downward displacement of air), since carbon(IV) oxide is denser than air.
Laboratory preparation of a dry sample of carbon(IV) oxide: marble chips and dilute HCl in the flask, the gas washed through water, dried over concentrated H₂SO₄, and collected by upward delivery in a gas jar.
(b)(i) I. Soil pollutant: pesticides (or excess fertilizers, polythene, oil spillage). II. Water pollutant: sewage/domestic waste (or factory effluent, crude oil). III. Air pollutant: sulphur(IV) oxide (or carbon(II) oxide, oxides of nitrogen, chlorofluorocarbons).
(ii) The major industrial use of sulphur(IV) oxide is in the manufacture of tetraoxosulphate(VI) acid, \( \text{H}_2\text{SO}_4 \), by the Contact process.
(c)(i) The molecules of petrol are held together by only very weak intermolecular forces of attraction. At room temperature the molecules already possess enough kinetic energy to overcome these weak forces, so they escape readily from the liquid surface into the vapour state; hence petrol is volatile.
(ii) Two criteria for purity: a pure substance has a sharp, constant melting point and a fixed, constant boiling point. (A fixed density or refractive index is also acceptable.)
(iii) I. Krypton: used in photographic flash lamps and fluorescent (fluorescent tube) lighting. II. Argon: used to provide an inert atmosphere in gas-filled electric light bulbs and in welding.
(d)(i) I. The colourless solution contains zinc tetraoxosulphate(VI), ZnSO₄.
II. Ionic equation: \( \text{Zn}_{(s)} + \text{Cu}^{2+}_{(aq)} \rightarrow \text{Zn}^{2+}_{(aq)} + \text{Cu}_{(s)} \).
III. On adding a few drops of sodium hydroxide solution, a white gelatinous precipitate of zinc hydroxide, \( \text{Zn(OH)}_2 \), is formed (which redissolves in excess sodium hydroxide).
(d)(ii) Volume of CO₂ produced from 5.3 g of Na₂CO₃:
