D. 1.0 (Total 1 mark) 2. The relative molecular mass of a gas is 56 and its empirical formula is CH 2. What is the molecular formula of the gas?

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Giles Parsons
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1 g of NaNO 3 (M r = 85) is dissolved in water to prepare 0.20 dm 3 of solution. What is the concentration of the resulting solution in mol dm 3? A B. 0.1 C. 0.2 D The relative molecular mass of a gas is 56 and its empirical formula is CH 2. What is the molecular formula of the gas? A. CH 2 B. C 2 H 4 C. C 3 H 6 D. C 4 H 8 3. What mass, in g, of hydrogen is formed when 3 mol of aluminium react with excess hydrochloric acid according to the following equation? A. 3.0 B. 4.5 C Al(s) + 6HCl(aq) 2AlCl 3 (aq) + 3H 2 (g) D. 9.0 IB Questionbank Chemistry 1

2 4. Chloroethene, C 2 H 3 Cl, reacts with oxygen according to the equation below. 2C 2 H 3 Cl(g) + 5O 2 (g) 4CO 2 (g) + 2H 2 O(g) + 2HCl(g) What is the amount, in mol, of H 2 O produced when 10.0 mol of C 2 H 3 Cl and 10.0 mol of O 2 are mixed together, and the above reaction goes to completion? A B C D What will be the concentration of sulfate ions in mol dm 3 when 0.20 mol of KAl(SO 4 ) 2 is dissolved in water to give 100 cm 3 of aqueous solution? A. 0.2 B. 1.0 C. 2.0 D The volume of an ideal gas at 27.0 C is increased from 3.00 dm 3 to 6.00 dm 3. At what temperature, in C, will the gas have the original pressure? A B C. 327 D. 600 IB Questionbank Chemistry 2

3 mol of a hydrocarbon with an empirical formula of CH 2 has a mass of 280 g. What is the molecular formula of this compound? A. C 2 H 4 B. C 3 H 6 C. C 4 H 8 D. C 5 H A toxic gas, A, consists of 53.8 % nitrogen and 46.2 % carbon by mass. At 273 K and Pa, g of A occupies 462 cm 3. Determine the empirical formula of A. Calculate the molar mass of the compound and determine its molecular structure. (Total 3 marks) 9. Brass is a copper containing alloy with many uses. An analysis is carried out to determine the percentage of copper present in three identical samples of brass. The reactions involved in this analysis are shown below. Step 1: Cu(s) + 2HNO 3 (aq) + 2H + (aq) Cu 2+ (aq) + 2NO 2 (g) + 2H 2 O(l) Step 2: 4I (aq) + 2Cu 2+ (aq) 2CuI(s) + I 2 (aq) Step 3: I 2 (aq) + 2S 2 O 3 2 (aq) 2I (aq) + S 4 O 6 2 (aq) (a) (i) Deduce the change in the oxidation numbers of copper and nitrogen in step 1. Copper: Nitrogen: IB Questionbank Chemistry 3

4 (ii) Identify the oxidizing agent in step 1. (1) (b) A student carried out this experiment three times, with three identical small brass nails, and obtained the following results. Mass of brass = g ± g Titre Initial volume of mol dm 3 S 2 O 2 3 (± 0.05 cm 3 ) Final volume of mol dm 3 S 2 O 2 3 (± 0.05 cm 3 ) Volume added of mol dm 3 S 2 O 2 3 (± 0.10 cm 3 ) Average volume added of mol dm 3 S 2 O 2 3 (± 0.10 cm 3 ) (i) Calculate the average amount, in mol, of S 2 O 2 3 added in step 3. (ii) Calculate the amount, in mol, of copper present in the brass. (1) (iii) Calculate the mass of copper in the brass. (1) IB Questionbank Chemistry 4

5 (iv) Calculate the percentage by mass of copper in the brass. (1) (v) The manufacturers claim that the sample of brass contains 44.2 % copper by mass. Determine the percentage error in the result. (1) (c) With reference to its metallic structure, describe how brass conducts electricity (1) (Total 10 marks) 10. Smog is common in cities throughout the world. One component of smog is PAN (peroxyacylnitrate) which consists of 20.2 % C, 11.4 % N, 65.9 % O and 2.50 % H by mass. Determine the empirical formula of PAN, showing your working. (Total 3 marks) IB Questionbank Chemistry 5

6 11. Which property increases down group 1? A. First ionization energy B. Melting point C. Reactivity D. Electronegativity 12. Which property generally decreases across period 3? A. Atomic number B. Electronegativity C. Atomic radius D. First ionization energy 13. Which pair of elements has the greatest difference in electronegativity? A. Cs and F B. Cs and Cl C. Cs and Br D. Cs and I IB Questionbank Chemistry 6

7 14. Which species has the largest radius? A. Cl B. K C. Na + D. K (i) Define the term first ionization energy of an atom. (ii) Explain the general increasing trend in the first ionization energies of the period 3 elements, Na to Ar. (iii) Explain why sodium conducts electricity but phosphorus does not. (Total 6 marks) 16. What is the correct Lewis structure for hypochlorous acid, a compound containing chlorine, hydrogen and oxygen? A. : Cl : O : H : B. : Cl : H : O : C. : Cl : O : H D. O : Cl : H 17. Which particles are responsible for electrical conductivity in metals? IB Questionbank Chemistry 7

8 A. Anions B. Cations C. Electrons D. Protons 18. The number of electrons in the valence shell of elements A and B, are 6 and 7 respectively. What is the formula and type of bonding in a compound formed by these elements? A. A 2 B, covalent B. AB 2, covalent C. A 2 B, ionic D. AB 2, ionic 19. Lewis structures are represented in different ways in different parts of the world. Two ways of drawing the Lewis structure for H 3 O + are shown below. Which statement is correct about H 3 O +? A. The ion has a tetrahedral shape. B. The H O H bond angle is 120. C. The H O H bond angle is 90. D. The ion has a trigonal pyramidal shape. IB Questionbank Chemistry 8

9 20. Predict the shape and bond angles for the following species: (i) CO 2 (ii) CO 3 2 (iii) BF 4 (Total 6 marks) 21. Describe and compare three features of the structure and bonding in the three allotropes of carbon: diamond, graphite and C 60 fullerene. (Total 6 marks) IB Questionbank Chemistry 9

10 1. B 2. D 3. D 4. A 5. D 6. C 7. D 8. empirical formula = CN; Working must be shown to get point. M r = 51.9 (g mol 1 ); :N C C N:; 3 [3] 9. (a) (i) Copper: 0 to +2 / increases by 2 / +2 / 2+; Allow zero/nought for 0. Nitrogen: +5 to +4 / decreases by 1 / 1 / 1 ; Penalize missing + sign or incorrect notation such as 2+, 2 + or II, once only. 2 IB Questionbank Chemistry 1

11 (ii) nitric acid/hno 3 / NO 3 /nitrate; Allow nitrogen from nitric acid/nitrate but not just nitrogen. 1 (b) (i) ; (mol); Award [2] for correct final answer. 2 (ii) (mol); 1 (iii) ( ) = g; Allow (iv) = % 1 (v) = 10/10.2 %; 44.2 Allow 11.3 % i.e. percentage obtained in (iv) is used to divide instead of 44.2 %. 1 (c) Brass has: delocalized electrons / sea of mobile electrons / sea of electrons free to move; No mark for just mobile electrons. 1 [10] 10. C N O H = 1.68 = = 4.12 = 2.48 ; = 2 = = 5 C 2 NO 5 H 3 ; = 3 ; No penalty for use of 12, 1 and/or 14. Award [1 max] if the empirical formula is correct, but no working shown. 3 [3] IB Questionbank Chemistry 2

12 11. C 12. C 13. A 14. B 15. (i) energy/enthalpy change/required/needed to remove/knock out an electron (to form +1 /uni-positive/ M +1 ion); in the gaseous state; Award for M(g) M + (g) + e. Award [2] for M(g) M + (g) + e with reference to energy/enthalpy change. 2 (ii) increasing number of protons/atomic number/z/nuclear charge; atomic radii/size decreases / same shell/energy level / similar shielding/ screening (from inner electrons); No mark for shielding/screening or shielding/screening increases. 2 (iii) Na: delocalized electrons / mobile sea of electrons / sea of electrons free to move; No mark for just mobile electrons. P: atoms covalently bonded / no free/mobile/delocalized electrons; 2 [6] 16. C 17. C 18. B IB Questionbank Chemistry 3

13 19. D 20. (i) (CO 2 ) linear; 180 ; 2 (ii) (CO 3 2 ) trigonal planar/triangular planar; 120 ; 2 (iii) (BF 4 ) tetrahedral; / 109 / ; 2 [6] IB Questionbank Chemistry 4

14 21. Award [2 max] for three of the following features: Bonding Graphite and C 60 fullerene: covalent bonds and van der Waals /London/ dispersion forces; Diamond: covalent bonds (and van der Waals /London/dispersion forces); Delocalized electrons Graphite and C 60 fullerene: delocalized electrons; Diamond: no delocalized electrons; Structure Diamond: network/giant structure / macromolecular / three-dimensional structure and Graphite: layered structure / two-dimensional structure / planar; C 60 fullerene: consists of molecules / spheres made of atoms arranged in hexagons/pentagons; Bond angles Graphite: 120 and Diamond: 109 ; C 60 fullerene: bond angles between ; Allow Graphite: sp 2 and Diamond: sp 3. Allow C 60 fullerene: sp 2 and sp 3. Number of atoms each carbon is bonded to Graphite and C 60 fullerene: each C atom attached to 3 others; Diamond: each C atom attached to 4 atoms / tetrahedral arrangement of C (atoms); 6 max [6] IB Questionbank Chemistry 5

1. The relative molecular mass of a gas is 56 and its empirical formula is CH 2. What is the molecular formula of the gas? D. C 4 H 8 (Total 1 mark)

1. The relative molecular mass of a gas is 56 and its empirical formula is CH 2. What is the molecular formula of the gas? A. CH 2 B. C 2 H 4 C. C 3 H 6 D. C 4 H 8 2. A fixed mass of gas has a certain