M(N) in compound M(compound). In option A the proportion is 14 = =

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1 hemistry einemann hemistry 1 5e Unit 1 Practice Exam 1 nswers Section Multiple-choice questions Question 1 Iodine is a covalent molecular substance where all electrons are localised either as a pair of bonding electrons or as lone pairs. opper and aluminium are metals where a lattice of cations is surrounded by delocalised electrons. Graphite is a layer lattice where 3 electrons per atom are localised in bonds and the 4th electron is delocalised. Question 2 Question 3 The proportion of N is given by it is M(N) in compound M(compound). In option the proportion is 17, in option or 40. Therefore, 16 represents the 28 or 16, in option it is 63 and in option it is 80 highest proportion of N. The formula of butane is Its molar mass is 58.1 g mol 1. So, in 2.70 g, n( 4 10 ) = = Number of molecules of 4 10 = = Question 4 Question 5 Question 6 Each molecule contains atoms, so total number of atoms = = stable ion with a charge of +3 is formed by elements with 3 electrons in their outer shell; 1s 2 2s 2 2p 6 3s 2 3p 1 has 3 electrons in the 3rd and outer shell, 2 in the 2s subshell and 1 in the 2p subshell. ne molecule has a mass of g, so 1 mole of molecules ( molecules) has a mass of = 42.1 g. Therefore, the molar mass of the compound is 42.1 g. The only compound with this molar mass is propene, and 2 are non-polar as there is no electronegativity difference between atoms of the same element. There is a slight electronegativity difference between and atoms in 4. verall, the 4 molecule is non-polar because of the tetrahedral symmetry of the molecule. While individual bonds in 2 are polar, the molecule is linear and the individual dipoles are cancelled out because of molecular symmetry. N 3, 2 S and l all contain polar bonds and in these molecules the individual dipoles are not cancelled out because the molecules are not symmetrical. opyright Pearson ustralia 2016 (a division of Pearson ustralia Group Pty Ltd) ISN Page 1

2 Question 7 Question 8 Question 9 Question 10 Question 11 Question 12 Question 13 Question Question 15 Question 16 The nitrogen atom has 5 electrons in the valence shell. nly 3 of the electrons are involved in bond formation in the N 2 molecule, leaving 2 electrons or 1 lone electron pair on each of the atoms in the N 2 molecule. There are a total of 2 lone electron pairs in the 2 molecule. First ionisation energy is highest in the top right-hand corner of the periodic table. It decreases down groups and increases from left to right across each period. ll atoms of copper have the same atomic number. owever, isotopes differ in the number of neutrons in the nucleus. The number of neutrons is the mass number minus the atomic number. So an atom of copper could have either 34 neutrons (63 29) or 36 neutrons (65 29). r is a polar molecule and forms dipole dipole bonds bond between r molecules. ipole dipole bonds formed between molecules where hydrogen is bonded to fluorine, oxygen or nitrogen are referred to as hydrogen bonds. ispersion forces, resulting from the attraction between instantaneous dipoles caused by the random movement of electrons, are also present in r. n ionic solid consists of ions in fixed positions. When molten, these ions are free to move and hence carry a current. Electronegativity is highest in the top left-hand corner of the periodic table. It decreases down groups and increases from left to right across each period. plasticiser consists of small molecules. These hold polymer chains further apart and so the dispersion forces between the polymer chains are decreased. This results in a more flexible polymer with a lower softening temperature. Given 1 nm = 10 9 m, in nm the radius of the hydrogen atom is The nucleus is very much smaller than the atom itself (the atom is mostly empty space). The radius of the nucleus is much less than half of the radius of the atom. X does not react with water so cannot be Na or a. Z does not react with dilute l, so cannot be Zn. u reacts with neither water nor dilute l. The recurring unit consists of 2 carbon atoms. ne carbon has 2 atoms attached and the other carbon has a 3 and a 3 group attached. It is the of the 3 that is attached to the second carbon. 3 3 opyright Pearson ustralia 2016 (a division of Pearson ustralia Group Pty Ltd) ISN Page 2

3 Section equals 1 mark Question 1 a. Mgl 2 l 2 (S 4 ) 3 Pb 2 b. iron(iii) nitrate ammonium chloride c. 1 mark for correct formula, 1 mark for appropriate use Some possible examples include a 3 as a building material, Na 3 as a rising agent in baking and (N 4 ) 2 S 4 as a source of nitrogen in fertilisers. Question 2 (6 marks) a. o: Fe has 26 protons, o 27 protons b. Li: electronegativity decreases down a group, so the first element has the highest electronegativity c. F : reactivity of non-metals decreases down a group so F is the most reactive and it forms an ion with a 1 charge d. Mg: 3 occupied shells indicates it is in period 3; 2 valence electrons indicates group 2; hence, Mg with electron configuration of 1s 2 2s 2 2p 6 3s 2 e. any element from Th to Lr: the actinides are the series of elements that follow actinium in the periodic table f. Ne: the noble gases are in group 18 Question 3 a. The atomic radius of potassium is larger. Potassium has 1 extra electron shell occupied. b. The strength of intramolecular bonding in the oxygen molecule is greater. The oxygen molecule has a double covalent bond between a pair of oxygen atoms. The water molecule has a weaker single bond between an oxygen and a hydrogen atom. c. The electrical conductivity of liquid potassium chloride is higher. Potassium chloride consists of ions which are free to move in the liquid state but propane consists of neutral molecules. Question 4 (4 marks) a. m(vitamin ) = 40.0 mg = g n(vitamin ) = m M = = mol b. number of molecules present = n N = = c. mass of oxygen in 1 mole of vitamin = = 96.0 g n() in 1 mole of vitamin = = 6 So each molecule of vitamin contains 6 atoms of oxygen. opyright Pearson ustralia 2016 (a division of Pearson ustralia Group Pty Ltd) ISN Page 3

4 Question 5 a. 1 mark for structure and 1 mark for corresponding name. i. one of the following: 2-methylpentane 3 3-methylpentane 3 3 2,2-dimethylbutane 3 2,3-dimethylbutane 3 3 ii. one of the following: propanoic acid methylethanoate ethylmethanoate opyright Pearson ustralia 2016 (a division of Pearson ustralia Group Pty Ltd) ISN Page 4

5 iii. one of the following: but-1-yne but-2-yne b. n unsaturated hydrocarbon is one that has one or more carbon to carbon double or triple bond. Question 6 a. methane b. chloromethane, methanol c. fluorine, nitrogen, oxygen, carbon dioxide d. graphite, ammonia, ethene e. fluorine, nitrogen, oxygen, carbon dioxide, methane, ethene f. ammonia, hydrogen fluoride, methanol g. hydrogen sulfide Question 7 a. i. 1 valence electron ii. in 5th shell s subshell (or 5s) b. i. onding is metallic. Structure is a lattice of rubidium cations surrounded by delocalised valence electrons. The lattice is held together by the electrostatic attraction between the cations and the delocalised electrons. (10 marks) ii. any correct use; for example, u for biological imaging, g as an antibacterial agent or in electronics 50.0 c. Fraction of 85 Rb isotope = = Fraction of 87 Rb isotope = = ( ) + ( ) so r (Rb) = 69.0 = 85.4 Question 8 a. m(i) in compound = = 27.2 g n(i) in compound = = 0.2 s the empirical formula is MI 2, n(m) in compound = = So, = M(M) and therefore M(M) = = 65.4 g mol 1 b. i. The metal is Zn (as it has a molar mass of 65.4 g mol 1 ). ii. 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 (6 marks) opyright Pearson ustralia 2016 (a division of Pearson ustralia Group Pty Ltd) ISN Page 5