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. Which element does not form a stable ion with the same electronic configuration as neon? Magnesium Fluorine Sodium Sulfur Sulfur is 2,8,6 so when it form an ion, it will be 2,8,8 which is the electron configuration of Argon 3 / 20 3. 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. 4 / 20 4. 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 5 / 20 5. 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 6 / 20 6. A student investigated the diffusion of ammonia gas, NH3, and hydrogen chloride gas, HCl. Two sets of apparatus were set up as shown below at room temperature and pressure. The damp red litmus paper in apparatus 1 changed colour after 30 seconds. How long does it take for the damp blue litmus paper to change colour in apparatus 2? about 21 seconds about 30 seconds about 64 seconds The blue litmus paper would not change colour. Molar mass of ammonia NH3 = 14+3 =17g molar mass of HCl = 1 +35.5 = 36.5 g HCl will take longer to diffuse as it has a higher molar mass 7 / 20 7. 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 8 / 20 8. 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 9 / 20 9. 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 10 / 20 10. Calcium nitrate crystals contain water of crystallisation. Its formula may be written as Ca(NO3)2●nH2O. When a 7.00 g sample of hydrated calcium nitrate is heated to remove all water, 4.90 g of anhydrous calcium nitrate remains after heating. What is the value of n? 1 2 3 4 7 g - 4.9 g = 2.1g of water 1 mole water --> 18g 2.1 g --> 0.11667 mole 1 mole Calcium nitrate --> 164g 4.9g --> 0.029878 mole ratio 0.029878 : 0.11667 1 : 4 11 / 20 11. 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 12 / 20 12. 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% 13 / 20 13. 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 14 / 20 14. 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 15 / 20 15. 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 16 / 20 16. 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 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. 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. 19 / 20 19. An unknown solid Q has the following properties. •When aqueous sodium hydroxide is added until in excess to the solution, no visible reaction is observed. • When dilute acid is added to Q, effervescence of a colourless gas is observed. • Q dissolves in water to form a colourless solution. • Q is stable to heat. What is Q likely to be? ammonium carbonate copper(II) hydroxide sodium carbonate zinc carbonate • When aqueous sodium hydroxide is added in excess to sodium carbonate, no reaction takes place • When dilute acid is added to sodium carbonate, carbon dioxide is evolved. • Sodium carbonate is soluble in water and form a colourless solution. • sodium carbonate is stable to heat. 20 / 20 20. Heavy water is made up of 2 deuterium( Hydrogen atoms with mass number 2) atoms and 1 oxygen atom. Which properties are true about heavy water? 1 Its boiling point is higher than 100 °C. 2. It reacts with sodium to form sodium hydroxide and hydrogen gas. 3 It can act as a solvent for sodium chloride. 1 only 2 and 3 only 1, 2 and 3 none of the above Heavy water has a higher molar mass as compared to normal water, and the boiling point will be slightly higher. Howeve,r most of the chemical properties will be similar. Your score isThe average score is 85% 0% Restart quiz
