O Levels Combined Chemistry G3 O Levels G3 Combined Chemistry Paper 1 mock Name 1 / 20 Which substances contain the same number of atoms? A B C D 2 / 20 Which of the following statements about a homologous series is correct? The melting and boiling point increases with increasing relative molecular mass. The members have similar physical properties. The members have the same molecular formula. The relative molecular masses of consecutive members differ by 12. The physical properties of members show a trend 3 / 20 A solution of a lithium halide and a halogen are mixed. A reaction occurs and the mixture darkens in colour. What are the reactants? bromine and lithium chloride iodine and lithium fluoride chlorine and lithium iodide chlorine and lithium fluoride Since the solution darken, there must be displacement. 4 / 20 When a 10 cm3 sample of a gaseous hydrocarbon was completely burnt in 35 cm3 of oxygen, the total volume of the products formed was 50 cm3. Which equation represents the combustion of the hydrocarbon? CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g) C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g) Since all the reactants and products are gases, we can use the ratio of volume directly without converting to moles. 10: 35 : 50 2 : 7 : 10 ratio of hydrocarbon is 2, ratio of oxygen is 7 and ratio of the sum of products is 10. Only D satisfy this ratio 5 / 20 Which of the following hydrocarbons would produce the sootiest flame when burnt in air? CH4 C4H10 C8H18 C12H26 The more C atoms in the molecule, the more soot (unburnt hydrocarbon) will be produced 6 / 20 An impure sample of calcium carbonate with a mass of 1.70 g was reacted with excess hydrochloric acid and 360 cm3 of carbon dioxide was collected at room temperature and pressure. What is the percentage purity of the calcium carbonate? 75% 88% 90% 98% CaCO3 + 2HCl --> CaCl2 + CO2 + H2O 1 mole --> 24000 cm3 360 cm3 --> 0.015 mole Ratio of CaCO3 : CO2 1:1 mole of CaCO3 = 0.015 mole molar mass of CaCO3 = 100g mass = 0.015 x 100 = 1.5g % purity = 1.5/1.7 x 100% = 88.2% 7 / 20 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 8 / 20 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 9 / 20 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 % 10 / 20 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 11 / 20 The flowchart shows some reactions of a compound T. What could compound T be? aluminium carbonate ammonium nitrate calcium nitrate zinc carbonate Ammonium salt + Strong Alkali --> ammonia gas + water + salt test for nitrate: add sodium hydroxide solution to the sample, followed by aluminum foil, and gently heat the mixture. If nitrate ions are present, they will be reduced to ammonia gas, which can be detected by its pungent smell or by its ability to turn damp red litmus paper blue. 12 / 20 50.0 cm3 of 0.10 mol/dm3 silver nitrate, AgNO3, is added to 150.0 cm3 of 0.05 mol/dm3 of sodium iodide, NaI, in a beaker. After the reaction, solid silver iodide is present in the beaker. What else is present in the mixture? Ag+, Na+, NO3- only Na+, I-, NO3- only Na+, I- only Na+, NO3- only AgNO3 + NaI --> NaNO3 + AgI 50.0 cm3 of 0.10 mol/dm3 silver nitrate, AgNO3 = 0.005 mole 150.0 cm3 of 0.05 mol/dm3 of sodium iodide, NaI, = 0.0075 mole Reactant ions left = Na+ and I - product ions = Na+ and NO3^- 13 / 20 Oxygen was prepared and collected using the apparatus as shown in the diagram below. The first tube of gas collected was discarded as it was contaminated. Which contaminant was in the gas? hydrogen hydrogen peroxide manganese(IV) oxide nitrogen There would be air in the test tube and tubing. Thus the main contaminant would be nitrogen gas. 14 / 20 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 15 / 20 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 16 / 20 Which statement is correct? 1.00 mol of zinc chloride contains 1.20 × 10^24 ions. 2.00 mol of sodium nitrate contains 1.20 × 10^24 ions. 24.0 dm3 of chlorine gas, measured at room temperature and pressure, contains 1.20 × 10^24 atoms. 48.0 dm3 of hydrogen gas, measured at room temperature and pressure, contains 1.20 × 10^24 atoms. 1 mole of any gas at rtp is 24 dm^3. therefore 24 dm^3 of chlorine gas has 1 mole of cl2 molecules which is 2 mole of atoms = 2 x 6 x10^23 = 1.2 x 10 ^24 17 / 20 Water is formed when oxygen combines with hydrogen. What mass of oxygen combines with 6 g of hydrogen? 12 g 48 g 96 g 144 g 2H2 + O2 --> 2H2O for H2, 1 mole --> 2g 6 g of hydrogen = 3 mole H2 : O2 2 : 1 3 mole : 1.5 mole 1.5 mole of O2 = 32 x 1.5 = 48g 18 / 20 In which equation does the metal oxide act as an acidic oxide? K2O (s) + H2O (l) → 2KOH (aq) Fe2O3 (g) + 3CO (g) → 2Fe (s) + 3CO2 (g) Al2O3 (s) + 6HCl (aq) → 2AlCl3 (aq) + 3H2O (l) PbO (s) + H2O (l) + OH− (aq) → Pb(OH)3− (aq) acidic oxide neutralises base/alkali to form salt and water CO is neutral. 19 / 20 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. 20 / 20 The diagram shows the apparatus used to separate hexane (boiling point, 70 oC) and heptane (boiling point, 98 oC). A B C D Heptane vapour will condense as it reaches the fractionating column; only hexane vapour will reach the condenser. As the thermometer will only measure the inlet of the condenser, the measured temperature will be constant at the boiling point of hexane until all the hexane has vaporized. Your score isThe average score is 85% 0% Restart quiz
