O Levels Combined Chemistry G3 O Levels G3 Combined Chemistry Paper 1 mock Name 1 / 20 1. 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 2 / 20 2. Which one of the following could be used to distinguish aqueous solutions of sodium chloride and sodium iodide? aqueous barium chloride aqueous silver nitrate aqueous sodium hydroxide aqueous sulfuric acid When silver nitrate is added, PPT of silver chloride(white) and silver iodide(yellow) will be formed, respectively 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. 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. 5 / 20 5. 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 6 / 20 6. Which of the following is the process by which a polyester is broken down into its monomers? condensation esterification hydrolysis polymerisation Hydrolysis of polymers is a chemical process where water molecules break down polymer chains 7 / 20 7. 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. 8 / 20 8. 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 9 / 20 9. 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. 10 / 20 10. A warship had its hull plated in copper to protect its wooden hull from rotting. However, after 2 years at sea, it was found that the iron parts of the warship in contact with the copper plates were more corroded than normal. What is the best explanation for this observation? Copper acts as a catalyst to speed up corrosion. Copper reacts with the iron to increase corrosion. Iron displaces copper to form iron(III) oxide. Iron is more reactive and corrodes in place of copper. Iron is above copper in the reactivity series. Iron will readily give away electrons to copper. Thus, iron will ionize easily to react with the oxygen in the air to rust. 11 / 20 11. 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 12 / 20 12. Which of the following statements about isotopes is correct? sotopes are atoms of the same element with the same number of protons but different number of electrons. Isotopes are atoms of the same element with the same number of protons but different number of neutrons Isotopes are atoms of the same element with the same number of neutrons but different number of electrons. Isotopes are atoms of the same element with the same number of neutrons but different number of protons. by definition, isotopes are atoms with the same number of protons and diff number of neutrons 13 / 20 13. Francium, Fr, is an element in the same group of the Periodic Table as lithium, sodium and potassium. Which statement about francium is likely to be correct? It forms a carbonate Fr2CO3. It forms coloured compounds. It reacts slowly with cold water. It is produced from the electrolysis of aqueous francium chloride. Use sodium or potassium as guide. Only extraction with electrolysis is true 14 / 20 14. 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. 15 / 20 15. 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. 16 / 20 16. 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 17 / 20 17. 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 18 / 20 18. Hydrogen gas reacts with chlorine gas to form hydrogen chloride gas. H2(g) + Cl2(g) → 2HCl(g) What is the final volume of the gas mixture when 20 dm3 of hydrogen is reacted with 30 dm3 of chlorine gas at 100 C? 40 dm3 50 dm3 60 dm3 70 dm3 H2(g) + Cl2(g) → 2HCl(g) hydrogen gas is limiting reagent. Cl2 gas is excess by 10 dm3 Vol of HCl produced = 2 x 20 dm3 = 40 dm3 Final volume = 40 + 10 = 50 dm3 19 / 20 19. 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 20 / 20 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% Your score isThe average score is 85% 0% Restart quiz
