O Levels Combined Chemistry G3 O Levels G3 Combined Chemistry Paper 1 mock Name 1 / 20 1. Lead(IV) chloride has a melting point of -15 °C and boiling point of 50 °C. Which type of structure do you expect lead(IV) chloride to have? a simple molecular structure with weak covalent bonds a simple molecular structure with weak intermolecular forces of attraction between molecules a giant molecular structure with strong covalent bonds between atoms a giant ionic crystal lattice structure with strong electrostatic forces of attraction Since the melting point and boiling point are low, it should be a simple molecular structure with weak intermolecular forces of attraction that can be overcome easily. 2 / 20 2. How many of the following processes will lead to an increase in greenhouse gas emissions? 1 2 3 4 decomposition -> give out carbon dioxide fermentation -> give our carbon dioxide photosynthesis -> take in carbon dioxide polymerisation -> none, maybe water respiration -> give out carbon dioxide neutralisation -> only salt and water 3 / 20 3. On adding 50 g of impure limestone, CaCO3 (Mr = 100), to excess hydrochloric acid, 6.0 dm3 of CO2 was evolved at room temperature and pressure. What is the percentage purity of the limestone? 25% 50% 75% 100% CaCO3 + 2HCl --> CaCl2 + CO2 + H2O for CO2: 24dm3 --> 1 mole 6 dm3 --> 0.25 mole mole ratio of CO2 : CaCO3 1 : 1 0.25 : 0.25 Molar Mass of CaCO3 = 100g 0.25 mole --> 25g Therefore, % purity = (25/50) x 100% = 50 % 4 / 20 4. When crude oil is fractionally distilled, which list best describes the mixture of compounds collected at the bottom of the fractionating column? Short chain molecules, low viscosity, high flammability Short chain molecules, low boiling point, low flammability Long chain molecules, high flammability, high boiling point Long chain molecules, high viscosity, high boiling point The molecules with the greatest molar mass and longest chain are collected at the bottom. They have the highest boiling point and are hard to ignite 5 / 20 5. A paper chromatography experiment was carried out to determine the inks present in a mixture, and the results shown below were obtained. Which statement about the results is incorrect? Ink 4 is more soluble than ink 3 in the solvent used. Inks 1 and 2 contained more than one colour pigment. The ink mixture contained inks 1, 3 and 4. The Rf value of ink 3 in the solvent used is more than 0.5. The further the ink moved from the starting line, the more soluble it is in this solvent 6 / 20 6. Which equations below represent redox reactions? 1. H+ + OH− → H2O 2. MnO4− + 8H+ + 5e− → Mn2+ + 4H2O 3. Cl2 + 2Br −→ Br2 + 2Cl − 1 only 3 only 1 and 2 only 2 and 3 only neutralisation ( not redox) redox redox 7 / 20 7. Aqueous hydrogen peroxide decomposes to form water and oxygen gas. Two experiments were carried out to measure the rate of production of oxygen from aqueous hydrogen peroxide. A B C D Experiment B has more starting reactant but lower concentration than A. Therefore, the curve will be less steep but finish higher. 8 / 20 8. An element T forms an ion, T2+, which has an electronic arrangement 2.8.8. Which statement(s) concerning T is/are correct? I T is an alkali metal. II T forms a basic oxide with oxygen. III T is in Period 4 of the Periodic Table. I and II only I and III only II and III only I , II and III Since its ion's charge is 2+, it is in group 2 and called Alkali Earth metal not alkali metal. 2,8,8,2 is calcium which is in period 4 as its atom have 4 electron shells. Its oxide is basic. 9 / 20 9. The structure of brass is shown below. What is the purpose of adding zinc to copper? to make the packing of atoms more compact to strengthen the metallic bonds between copper atoms to prevent layers of copper atoms from sliding over each other easily to prevent the ‘sea of electrons’ from moving freely in the metal lattice Adding zinc atoms to copper disrupts the orderly arrangement, which prevents layers of copper atoms from sliding over each other easily. The effect is that the alloy is now harder and stronger than pure copper. 10 / 20 10. When excess aluminium oxide, Al2O3 was added to a portion of dilute sodium hydroxide. Which of the following correctly describes the pH change and the explanation? A B C D Aluminium oxide is amphoteric and neutralises the sodium hydroxide. Thus the pH decrease 11 / 20 11. Which statement does not explain why the speed of the reaction between zinc and dilute sulfuric acid increases when the acid is warmed? The particles are moving faster as they gain more energy. The activation energy of the reaction decreases. The particles are colliding more frequently. More particles have sufficient energy required for the reaction. An alternative pathway with lower activation energy is only provided by a catalyst, not a higher temperature 12 / 20 12. Which statement explains why sodium chloride, NaCl, has a lower melting point than magnesium oxide, MgO? Sodium chloride has a simple molecular structure while magnesium oxide has a giant ionic structure. Sodium is more reactive than magnesium. The attraction between Na+ and Cl− is weaker than that between Mg2+ and O2−. The particles in sodium chloride are more closely packed than in magnesium oxide. Both compounds are giant ionic structures. But the magnesium ion charge is 2+ while the sodium ion is 1+. Thus, the electrostatic forces holding the ions together are stronger in magnesium chloride 13 / 20 13. Which compound has the lowest percentage by mass of nitrogen? (NH2)2CO (NH4)2SO4 (NH4)3PO4 NH4NO3 % of N in (NH2)2CO = 46.65 % % of N in (NH4)2SO4 = 21.2% % of N in (NH4)3PO4 = 28.18% % of N in NH4NO3 = 35% 14 / 20 14. The following chemicals are available in the laboratory. aqueous bromine Universal Indicator solution magnesium powder sodium carbonate Which of these chemicals can be used to distinguish between propene and propanoic acid? All of them 1 only 1 and 4 only 1, 2 and 3 only aqueous bromine --> change colourless/no change Universal Indicator solution --> turns orange/ green magnesium powder --> no change/effervescence sodium carbonate --> no change/effervescence 15 / 20 15. Which diagram best represents the structure of calcium oxide? A B C D Ca is cation and O is anion. They are opposite in charge and attract each other. Thus in the diagram, only black balls are bonded to white balls directly. 16 / 20 16. Three elements W, X, Y, and Z have consecutive, increasing proton (atomic) numbers. Element Y exists as a colourless, monatomic gas at room temperature. Which will be the chemical formula of a compound formed between W and chlorine? WCl W2Cl WCl2 W2Cl3 Y would be noble gas and thus W is in group 16 with 6 valence electrons and need 2 more Cl has 7 valence and need 1 more so the formula will be WCl2 17 / 20 17. Ammonia and excess carbon dioxide can react to form urea and water in a reaction. 2NH3 + CO2 → CON2H4 + H2O The percentage yield of this reaction is 80 %. What is the mass of ammonia required for this reaction to obtain 60.0 g of urea? [Mr: NH3, 17; CO2, 44; CON2H4, 60; H2O, 18] 10.6 g 27.2 g 34.0 g 42.5 g Molar mass of urea = 60g --> 1 mole 100/80 x 1 = 1.25 mole of urea mole of ammonia = 1.25 x 2 = 2.5 mole mass of ammonia = 2.5 x 17g = 42.5g 18 / 20 18. An unknown substance X starts melting at –180 °C and finishes melting at –160 °C. What is substance X likely to be? a compound a mixture an element insufficient data to determine Pure compounds and elements will have a fixed melting point. Only mixtures melt over a range 19 / 20 19. CH4, H2O and HCl are covalent compounds. Which atoms in these compounds do not use all their outer shell electrons in bonding? C and H C and O O and Cl Cl and C O has 6 valence electrons and only uses 2 for bonding Cl has 7 valence electrons and only uses 1 for bonding 20 / 20 20. Which of these Group 1 elements reacts most violently with water? caesium lithium potassium rubidium reactivity increases as it goes down the group. Your score isThe average score is 85% 0% Restart quiz
