Further exercises

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For page 9

A1. Some samples of air are homogeneous while others are heterogeneous. Explain how this is possible.
 
A2. (a) Can a mixture be homogeneous? If so give an example. Explain fully.
(b) Can a pure substance be heterogeneous? If so give an example. Explain fully.
 
A3. When some silvery aluminium turnings were mixed with powdered yellow sulfur and the mixture heated, a white homogeneous solid formed. On cooling it remained as a white solid. When heated again, it underwent no apparent change. When the experiment was repeated several times using different masses of aluminium turnings and sulfur, the white solid always contained 36% aluminium. Is the white solid a mixture or a compound? Explain why.
 

For pages 16 and 20
Some of the exercises in this set require techniques described in the Supplementary Material section above.

B1.  Brandy (about 40% ethanol) is made by distilling wine (12 to 14% ethanol). In such a distillation is the brandy the distillate or is it the liquid left in the distillation flask? Explain. If you distilled some brandy, would the distillate contain a higher or lower percentage of ethanol than the original brandy? Explain.
 
B2.2.  A student accidentally poured an aqueous solution of silver nitrate into a bottle of kerosene. How would you recover the aqueous solution?
 
B3.  When air (after removal of moisture and carbon dioxide and impurities) is cooled to 210oC, a homogeneous liquid mixture (solution) of nitrogen and oxygen forms. If this mixture is slowly warmed until it starts to boil, what would you expect the vapour formed to be pure oxygen, pure nitrogen, or a mixture? If a mixture how would its composition compare with that of the liquid? How could you obtain a sample of one pure substance from the original liquid and what substance would it be? Again use Table1.8 on page 23 to answer this question. Note that there should be minus signs in front of the boiling points of oxygen, nitrogen and hydrogen, that is 183, 196 and 253oC.
 
B4.  In a school laboratory a new supply of small lead pellets was accidentally put into a jar containing iron filings. How would you separate the lead from the iron? More than one way may be possible.
 
B5. How would you separate a mixture of (a) sand and iodine (neither has a significant solubility in water) (b) sodium chloride and ammonium chloride (both are soluble in water).
 
B6. When a solution of ammonia was added to a solution of copper sulfate, the resulting mixture had an intense dark blue colour. When a solution of sodium hydroxide was added to a solution of copper sulfate, the resulting mixture had a pale blue milky appearance. Both mixtures remained unchanged for many minutes. Then both mixtures were centrifuged. The deep blue mixture remained unaltered, but the pale blue one separated into a clear solution and a pale blue solid at the bottom of the centrifuge tube. Which, if either, of the original mixtures was heterogeneous and which, if either, was a solution? Explain why.
 
B7. How would you separate a mixture of carbon, iodine and ammonium chloride. Ammonium chloride is readily soluble in water but insoluble in hexane; iodine is readily soluble in hexane but only slightly soluble in water while carbon is insoluble in both solvents. Both iodine and ammonium chloride sublime.
 

For page 24

C1. (a) At room temperature (20oC), which of the substances in Table 1.8 on page 23 are (i) solid (ii) liquid (iii) gas?
(b)  Which if any of these substances would undergo a change of state if the temperature was (i) lowered to 2oC (ii) raised to 100oC?
 

For page 25

D1. To determine the density of lead a pair of students took some lead shot (pellets), determined their mass then poured them into a burette containing some water. They noted the reading on the burette before and after adding the lead pellets. Use their results below to determine the density of lead.
Mass of lead pellets taken = 142.6 g
Initial reading of the burette = 34.7 mL
Burette reading after adding the lead shot = 22.2 mL
 
D2. Explain how you would determine the density of a fine gold chain (necklace). How could you use your answer to decide whether the chain was solid gold or just gold plated copper. You may use data in Table 4.4 on page 110.
 

For page 27

E1. Each tablet of the Alka Seltzer shown in the photo on page 26 contains 
324 mg aspirin, 1.9 g sodium bicarbonate and 1.05 g citric acid. Calculate the per cent composition of this mixture.
 
E2. To determine the composition of bagged dry concrete mix (crushed rock,  sand, cement), a pair of students used a set of shop scales to weigh out a sample of the mixture (3.23 kg). They then used a coarse sieve to separate out the crushed rock (aggregate) then weighed the separated rock (1.85 kg). They then used a fine sieve to separate the sand from the cement. Using laboratory scales they found that the sand has a mass of 910 g and the cement 420 g. Determine the percentage composition of the dry concrete mix.
 
E3. In Exercise E2 above why do you think the sum of the masses of the separated components was less than the starting mass? Suggest another source of error in this experiment. How would it affect the results? How could the experiment be modified to give more accurate results?
 
E4. Chalcocite is a mineral of copper (not a common one in Australia). It is a compound containing copper and sulfur. When carefully heated in air black chalcocite decomposes to reddish brown copper (with the sulfur vaporising as sulfur dioxide). A 2.36 g sample of chalcocite formed 1.89 g copper. Calculate the percentage copper in chalcocite.
 
E5. Brass is an alloy (solid solution) of copper and zinc. To determine the composition of a sample of brass filings a chemist mixed 1.72 g of the filings with warm hydrochloric acid; this dissolved the zinc but left the copper unaffected. After complete reaction (no further evolution of gas) the remaining solid was filtered off and weighed: it had a mass of 0.92 g. Calculate the percentage copper in that particular brass.
 
E6. The experiment in Exercise E5 was repeated on three other samples of brass. Use the results below to show that brass is a mixture and not a compound.
Mass of sample used (g) 1.38 2.04 1.87
Mass of copper left (g) 0.81 1.00 1.05

There are no F exercises

For page 48

G1. Molecular formulae for some everyday substances are given below.
(a) How many atoms of each type are present in a molecule of each of these substances?
(b) What is the total number of atoms in each of these molecules?
(i) boracic acid or boric acid (disinfectant), B(OH)3
(ii) acetic (ethanoic acid) (in vinegar), CH3COOH
(iii) urea (common nitrogenous fertiliser), CO(NH2)2
(iv) ascorbic acid (Vitamin C), C6H4O2(OH)4
 
G2. Write molecular formulae for the compounds below. The number of each type of atom present in the molecule is given:
(a) Refrigerant 134a (currently used in air conditioners); 2 carbon, 
2 hydrogen and 4 fluorine atoms
(b) Cysteine, on of the essential amino acids; 3 carbon, 7 hydrogen, 
2 oxygen 1 sulfur and 1 nitrogen atoms
(c) peroxyacetyl nitrate, a constituent of photochemical smog; 2 carbon, 
3 hydrogen, 1 nitrogen and 4 oxygen atoms
 

For pages 52 and 55

H1. What are the atomic and mass numbers of the element in which the atoms contain
(a) 14 protons and 15 neutrons
(b) 42 neutrons and 33 electrons
(c) 22 neutrons and 18 protons
(d) 12 electrons and 12 neutrons
Name, and give the symbol for, each of these four elements.
 
H2. Two atoms each have 12 protons in the nucleus: one has 12 neutrons while the other has 13. How many electrons do each of these atoms contain? Do these two atoms belong to the same or different elements? Explain.
 
H3. Using Figure 2.9(b) on page 53 as a guide, give the electron configuration of the following elements (atomic number in brackets): Sr (38), Zr (40), Tc (43), Sb (51), Xe (54).
 
H4. Give the electron configuration of O, S, Se and Te for which the atomic numbers are 8, 16, 34 and 52. What common feature is there about these four configurations?
 

For page 58

J1. Write down the electron configurations of elements having atomic numbers 
9, 3, 12, 18, 15, 4, 20, 30, 13, 36, 6, 16. State which group of the Periodic Table each belongs to.
 
J2.

Use the Periodic Table to predict how many electrons there are in the outermost energy level (shell) of the following atoms:
barium, bromine, gallium, arsenic, caesium, selenium
 

J3.

We often talk about the electron configuration of monatomic ions. To obtain the electron configuration of an ion, we start with the configuration of the atom and add or subtract the necessary number of electrons to form the ion. We add electrons to the next available positions in the energy levels and we remove them from the highest energy level (last in, first out!). Hence give the electron configuration of the following, taking atomic numbers from the Periodic Table if necessary

(a) potassium atom, potassium ion
(b) fluorine atom, fluoride ion
(c) aluminium atom, aluminium ion
(d) sulfur atom, sulfide ion
 
J4. (a) Write down the electron configuration of the members of each of the following sets of atoms and ions:
(i) O2, F, Ne, Na+, Mg2+
(ii) S2, Cl, Ar, K+, Ca2+
(b) What do all five species in each set have in common? Why is this so?
 

For page 61 and 65

K1. Draw diagrams similar to those in Examples 1 and 2 on pages 59 and 60 to show the formation of ionic bonds involving 
(a) lithium and bromine 
(b) magnesium and sulfur 
(c) sodium and oxygen
 
K2.

 Using a Periodic Table, deduce the electron configuration of, and the charge on, the ions you would expect to be formed by:

(a) strontium 
(b) iodine

(c) rubidium
(d) selenium
 

K3. Draw electron dot diagrams and give the molecular formulae for covalent molecules formed between 
(a) chlorine and iodine 
(b) hydrogen and sulfur 
(c) phosphorus and fluorine
 
K4. Hydrogen and nitrogen are able to form the negative hydride and nitride ions respectively. Draw electron dot structures for these two ions, showing clearly the charge on each. Sodium can form both a hydride and a nitride; what formulae do you expect for these compounds?
 
K5. Which of the following compounds would you expect to be ionic? Explain why, and draw electron dot diagrams of the ions present, and give the formulae of the compounds:
(a) magnesium chloride
(b) sulfur dichloride
(c) barium oxide
(d) nitrogen triiodide 
(e) sodium sulfide 
(f) boron trifluoride
(g) calcium chloride
(h) potassium iodide
(i) oxygen fluoride
(j) iodine chloride
 
K6. Which of the compounds in Exercise K5 would you expect to be covalent? Draw electron-dot diagrams for them and give their molecular formulae.
 

For pages 68 and 73

L1. Arsenic tribromide and magnesium bromide are white solids at room temperature. The solids melt at 31oC and 711C respectively. As liquids, magnesium bromide conducts electricity while arsenic tribromide does not. Explain the difference in melting points and conductivities in terms of the bonding in the two substances.
 
L2. Tungsten carbide (carborundum) is an extremely hard substance (comparable to diamond) with a very high melting point, 2870oC. it does not conduct electricity and is insoluble in all common solvents. What do you conclude about its structure?
 
L3. Tin forms two distinct compounds with chlorine, SnCl2 and SnCl4. SnCl2 is a solid at room temperature while SnCl4 is a liquid. The melting point of SnCl2 is 247C and the boiling point of SnCl4 is 113C. Liquid SnCl2 conducts electricity while liquid SnCl4 does not.
(a) What do you conclude about the bonding in SnCl2 and SnCl4? Give your reasoning.
(b) For any ionic compound(s) state what ions you expect to be present. For any covalent compound(s) draw an electron-dot diagram. Again give reasons for your conclusions.
 
L4. Use the Periodic Table to answer the following:
(a)

Sodium chloride, oxide, fluoride and sulfide have the formulae, NaCl, Na2O, NaF, Na2S. What do you expect to be the formulae of:
(i) rubidium chloride and oxide,
(ii) caesium fluoride and sulfide?

(b) Sodium reacts with water to form hydrogen gas. Name three other elements you would expect to react with water to form hydrogen.
(c) Magnesium and calcium form chlorides, MgCl2 and CaCl2. What compounds do you expect fluorine, bromine and iodine to form with magnesium and calcium?
(d) Fluorine forms with carbon the compound carbon tetrafluoride, CF4. What compounds do you expect chlorine and bromine to form with carbon?
(e) Oxygen and nitrogen with hydrogen form the compounds, water, H2O and NH3 respectively. Give the formulae you would expect for the compounds formed between sulfur and hydrogen and between phosphorus and hydrogen.
 
L5.

Some properties of six substances that are solids at room temperature are listed below. Which (if any) of these would you consider to be a (a) metals 
(b)
ionic lattices (c) covalent molecular substances (d) covalent lattices? 
Give your reasons for each. 

  Melting point (oC) Does it conduct electricity? Other properties
as a solid as a liquid
L 63 yes yes soft and malleable
M 44 no no soft and crumbly
N 2990 no no extremely hard
P 2045 no yes very hard
Q 725 yes yes hard but can be rolled into sheets
R 373 no yes moderately hard but can be ground into a powder

 
For pages 81 and 87

M1. 1.00 g of a pale blue solid was heated strongly in a crucible open to the atmosphere; it changed to a black solid which weighed 0.64 g. After being allowed cool down and stand on the bench for several hours, there was no further change in the appearance or mass of the black solid. Explain why there has been a decrease in mass. Is this a chemical or physical change? Why? Was the original pale blue solid an element or a compound? Explain why. 
 
M2. (a) Classify the italicised substances mentioned in the passage below as mixtures, elements or compounds. In many cases the information in the passage will help you with the classification.
(b) Identify three chemical and three physical changes in the passage and give your reasons for so identifying them.
Aluninium is a substance in widespread use today in building materials, aircraft construction and household utensils. Aluminium is obtained from bauxite a red brown granular material composed of variable amounts of aluminium oxide, iron oxide and silicaceous material (dirt).
The bauxite is ground up very finely then treated with hot concentrated sodium hydroxide solution. This reacts with the aluminium oxide to form a solution of sodium aluminate. The insoluble iron oxide and dirt are filtered off and disposed of as red mud. Aluminium oxide is recovered by cooling the sodium aluminate solution to precipitate out aluminium hydroxide which is filtered off and heated to form aluminium oxide.
The pure white aluminium oxide known as alumina is then sent to an aluminium smelter where an electric current is passed through a molten mixture of alumina and cryolite a substance containing sodium, aluminium and fluorine in fixed proportions. This process, called electrolysis, breaks the aluminium oxide into aluminium and oxygen. However rather than forming oxygen gas the electrolysis causes the oxygen to combine with the graphite of the electrode to form carbon dioxide.
The sodium aluminate mentioned above is also formed onaluminium utensils cleaned in automatic dishwashers. Dishwashing powder contains variable amounts of detergent, bleaches and sodium hydroxide. The latter substance attacks aluminium to form the aluminate which discolours the utensils.
 

For pages 91 and 94

N1. Name the following compounds:
(a) SO3
(b) MgH2
(c) Li2S
(d) As2O3
(e) CF4
(f) Al2O3
(g) CuS
(h) NO2
(i) S2Cl2
(j) FeCl3
(k) Cl2O7
(l) Zn(OH)2
 
N2. Write the formulae of the following compounds:
(a) (i) 
(ii) 
(iii)
(iv)
(v)
(vi)
potassium oxide
dichlorine trioxide
antimony pentafluoride
aluminium hydroxide
silver oxide
iodine trichloride
(vii)
(viii)
(ix)
(x)
(xi)
(xii)
diphosphorus trisulfide
iron(III) sulfide
silicon tetrabromide 
iron(II) chloride
magnesium hydride
sulfur hexafluoride
(b) (i)
(ii)
(iii)
magnesium nitrate
silver carbonate
ammonium sulfate
(iv)
(v)
(vi)
iron(III) sulfate
aluminium phosphate 
lead(IV) chloride
 

Answers to Exercises

A1. If the air is clean (just a mixture of gases) then it is homogeneous: if it contains dust particles or water droplets (fog), it is heterogeneous.
A2. (a) Yes; solution of sugar in water, honey, whiskey
(b) No; by definition (Table 1.1 page 6) a pure substance must be homogeneous. It is tempting to think of a glass of water with ice in it as a pure substance, but by our definition it is not because there are two phases present, liquid and solid.
A3. Compound; because its properties are different from those of the starting substances (elements), it does not easily revert to the starting elements and it has constant composition.
B1. Distillate, because the distillate is richer in the more volatile component (the one with the lower boiling point) which is ethanol (alcohol). Higher, same reason.
B2. Allow the two liquids to settle and separate (they are immiscible, then use a separating funnel (page16-17).
B3. A mixture; richer in nitrogen (the one with the lower boiling point); fractionally distil it (page 15), nitrogen
B4. Use a magnet: iron attaches to it, lead does not.
B5. (a) By sublimation; put the mixture in a flask fitted with a cooled test tube as in the photo on page 78; the iodine sublimes on to the cold surface and the sand remains on the bottom of the flask.
(b) Again by sublimation; this time the ammonium chloride vaporises and condenses on the cooled surface.
B6. The milky mixture resulting from adding sodium hydroxide solution to copper sulfate solution is heterogeneous, because it can be separated into a solid and a liquid (solution) by centrifuging; the two solutions reacted to form copper hydroxide, a pale blue solid. The mixture of copper sulfate and ammonia solutions is a true solution: it cannot be separated by centrifuging; the change in colour results from a chemical reaction between the two solutions to form the deep blue solution of a new compound called tetraamminecopper(II) sulfate (or copper tetrammine sulfate).
B7. Add hexane to dissolve the iodine, filter to separate the solids from the iodine in hexane solution. Evaporate off the hexane to recover solid iodine. Then sublime the carbon, ammonium chloride mixture as in answer B5.
Alternatively you could add water to the original mixture to dissolve the ammonium chloride then after filtration separate the carbon and iodine by sublimation.
Still another method would be to separate the iodine by dissolving it in hexane and filtering it off, then adding water to the carbon, ammonium chloride mixture to dissolve the latter and so separate that pair. 
C1. (a) Oxygen, nitrogen and hydrogen are gases, water, ethanol, ethyl acetate, ethylene glycol, acetic acid, chloroform and hexane are liquids and the rest are solids.
(b) (i) Water and acetic acid would change to solids
(ii) Sodium and phosphorus would change from solid to liquid; water, ethanol, ethyl acetate, chloroform and hexane would change from liquid to gas (vapour).
D1. 11.4 g/mL
D2. Determine its mass then measure its volume by dropping it into a burette partly filled with water and observing the change in volume (as in exercise D4). If it was gold plated copper its density would be about 9 g/mL. If it was pure gold (24 carat) its density would be 19.3 g/mL. If it was 18 or 9 carat gold its density would be about 17 or 13 g/mL respectively. Density would clearly distinguish between gold plated copper and any of the common gold alloys.
E1. 10% aspirin, 58% sodium bicarbonate, 32% citric acid
E2. 57% aggregate, 28% sand, 13% cement. There has been a 1.5% loss of material during the analysis so it is not as accurate as the measured masses suggest: hence the rounding off in the percentages.
E3. There was some loss of material as dust into the air or stuck to the sieves, or even perhaps some spillage. Some cement would have stayed with the aggregate and sand (stuck on the surface of those coarse particles). This would have meant that the percentage of cement was low. After separating the aggregate and sand wash each with water to remove the cement, remove the solution/suspension of cement in water by sedimentation and decantation (page 13), dry the aggregate and sand then re-weigh each. This would give more accurate measures of the amounts of aggregate and sand; take the true mass of cement as the difference between starting mass and mass of aggregate plus sand.
E4. 80.1%
E5. 53.5% copper
E6. The percentage copper in the three samples is 58.7%, 49.0% and 56.1% (left to right). Combined with the answer in exercise E5, we have clear evidence that the composition of brass is variable. Therefore brass is a mixture (solid solution) and not a compound.
F1. Because they do not agree with the law of conservation of matter (page 31); mass of products is 1.25 g compared with 1.36 g of starting material.
F2. 1.43 g; law of conservation of mass says that the mass of products must equal the mass of reactant.
G1. (a) (i)
(ii)
(iii)
(iv)
1 boron, 3 oxygen and 3 hydrogen atoms
2 carbon, 4 hydrogen and 2 oxygen atoms
1 carbon, 4 hydrogen, 1 oxygen and 2 nitrogen atoms
6 carbon, 8 hydrogen, and 6 oxygen atoms
(b) (i) 7 (ii) 8 (iii) 8 (iv) 24
G2. (a) C2H2F4
(b) C3H7O2SN
(c) C2H3O5N
H1. atomic numbers: (a) 14 (b) 33 (c) 18 (d) 12
mass numbers:(a) 29 (b) 75 (c) 40 (d) 24
Names and symbols: (a) phosphorus, P (b) arsenic, As (c) argon, Ar 
(d)
magnesium, Mg
H2. Both have 12 electrons; same element (It is the number of protons that determines which element an atom belongs to: as we shall see on page 141 these two atoms are isotopes of the one element.
H3. Sr (2, 8, 18, 8, 2)
Zr (2, 8, 18, 10, 2)
Tc (2, 8, 18, 13, 2)
Sb (2, 8, 18, 18, 5)
Xe ( 2, 8, 18, 18,8)
H4. O (2, 6) S (2, 8, 6) Se (2, 8, 18, 6) Te (2, 8, 18, 18, 6);They all have six electrons in their outermost energy level (that is, six valence electrons).
J1. 9: (2, 7) Group 7
3: (2, 1) Group 1
12: (2, 8, 2) Group 2
18: (2, 8, 8) Group 0 (or 8)
15: (2, 8, 5) Group 5
4: (2, 2) Group 2
20: (2, 8, 8, 2) Group 2
30: (2, 8, 18, 2
13: (2, 8, 3) Group 3
36: (2, 8, 18, 8) Group 0 (or 8)
6: (2, 4) Group 4
16: (2, 8, 6) Group 6
J2. barium, 2
bromine, 7
gallium, 3
arsenic, 5
caesium, 1
selenium, 6
J3. (a) K (2, 8, 8, 1); K+ (2, 8, 8)
(b) F (2, 7); F (2, 8)
(c) Al (2, 8, 3) ; Al3+ (2, 8)
(d) S (2, 8, 6); S2 (2, 8, 8)
J4. (a) (i) all are (2, 8)
(ii) all are (2, 8, 8)
(b) They all have a stable noble gas configuration; because atoms tend towards the configuration of the noble gas nearest to them.
K1. Your diagram should show:
(a) a lithium atom with configuration (2, 1) donating an electron to a bromine atom (2, 8, 18, 7) to form Li+ (2) and Br (2, 8, 18, 8)
(b) a magnesium atom (2, 8, 2) donating 2 electrons to a sulfur atom 
(2, 8, 6) to form Mg2+ (2, 8) and S2 (2, 8, 8)
(c) each of two sodium atoms (2, 8, 1) donating one electron to the same oxygen atom (2, 6) to form two Na+ (2, 8) ions and one O2 (2, 8) ions
K2. (a) Sr2+ (2, 8, 18, 8) (b) I (2, 8, 18, 18, 8) (c) Rb+ (2, 8, 18, 8) 
(d)
Se2 (2, 8, 18, 8)
K3.

K4.
NaH, Na3N
K5. Ionic: a, c, e, g, h
Mg2+, Ba2+, Na+, Ca2+ , K+ (electron-dot diagrams show only valence electrons (outer shell electrons): positive ions are formed by the atoms giving away all the valence electrons, so their diagrams have no electrons on them.)

K6. covalent: b, d, f, i, j
L1. Arsenic tribromide is a covalent molecular compound while magnesium bromide is ionic; ionic compounds consist of an infinite lattice of positive and negative ions: this is hard to break up so ionic compounds have high melting points. However once molten there are mobile ions present that are able to move under the influence of an electric voltage and so ionic compounds conduct electricity.
Covalent molecular compounds consist of discrete small molecules with only weak intermolecular forces between them; hence they melt at low temperatures. These molecules are neutral so such substances do not conduct electricity.
L2. It is a covalent lattice
L3. (a) Ionic in SnCl2 and covalent in SnCl4; similar reasoning to that given in the answer to exercise L1.
(b) In SnCl2: Sn2+ and Cl
L4. (a) (i) RbCl, Rb2O
(ii) CsF, Cs2S
(b) Lithium, potassium, rubidium and caesium
(c) MgF2, MgBr2, MgI2, CaF2, CaBr2, CaI2
(d) CCl4 and CBr4
(e) H2S, PH3
L5. (a L and Q; both are conductors as solids and both are malleable
(b) P and R; conduct electricity as liquids but not as solids, relatively high melting points, hard and/or brittle
(c) M; low melting point, does not conduct electricity either as a solid or as a liquid, soft
(d) N; very high melting point, does not conduct electricity, extremely hard
M1. A gas has been formed; chemical, because two new substances have been formed (the black solid and the invisible gas), and the change does not easily reverse. The original solid was a compound, because it decomposed into two other substances.
M2. (a) Mixtures: bauxite, sodium hydroxide solution, solution of sodium aluminate, red mud, dishwashing powder
Elements: aluminium, graphite (carbon)
Compounds: aluminium oxide, iron oxide, aluminium hydroxide, cryolite, carbon dioxide, sodium hydroxide (as a solid)
(b) Chemical: (i) reaction of hot concentrated sodium hydroxide with aluminium oxide, (ii) conversion of sodium aluminate to aluminium hydroxide, (iii) heating the aluminium hydroxide to form aluminium oxide, (iv) electrolysis of alumina to form aluminium, (v) reaction of oxygen with graphite to form carbon dioxide, (vi) attack of sodium hydroxide on aluminium (in dishwashers)
Physical: (i) grinding up the bauxite, (ii) filtering off the red mud, (iii) filtering off the aluminium hydroxide (iv) mixing alumina and cryolite to form a solution (homogeneous molten mixture)
M3. (a) P2O5(s) + 3H2O(l) 2H3PO4(l)
(b) 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)
M4. (a) Two atoms of solid arsenic react with five diatomic molecules of liquid bromine to form two molecules of solid arsenic pentabromide.
(b) One molecule of gaseous dichlorine heptoxide reacts with one molecule of liquid water to form two molecules of liquid perchloric acid, each molecule of which contains one hydrogen, one chlorine and four oxygen atoms.
N1. (a)sulfur trioxide
(b) magnesium hydride
(c) lithium sulfide
(d) diarsenic trioxide (arsenic trioxide is acceptable)
(e) carbon tetrafluoride
(f) aluminium oxide
(g) copper sulfide (copper(II) sulfide is also acceptable)
(h) nitrogen dioxide
(i) disulfur dichloride
(j) iron(III) chloride
(k) dichlorine heptoxide
(l) zinc hydroxide
N2. (a) (i) K2O (v) Ag2O (ix) SiBr4
(ii) Cl2O3 (vi) ICl3 (x) FeCl2
(iii) SbF5 (vii) P2S3 (xi) MgH2
(iv) Al(OH)3 (viii) Fe2S3 (xii) SF6
(b) (i) Mg(NO3)2 (iii) (NH4)2SO4 (v) AlPO4
(ii) Ag2CO3 (iv) Fe2(SO4)3 (vi) PbCl4