O Levels Combined Chemistry G3 O Levels G3 Combined Chemistry Paper 1 mock Name 1 / 20 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. 2 / 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 3 / 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 4 / 20 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 5 / 20 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 6 / 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. 7 / 20 Which property of elements increases from left to right of Period 3 of the Periodic Table? number of outer shells metallic character tendency to get reduced melting points As you move from left to right across a period, the number of protons in the nucleus increases, which leads to a stronger attraction for electrons. This increased attraction makes it more difficult for an atom to lose electrons, 8 / 20 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 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 10 / 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 11 / 20 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. 12 / 20 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. 13 / 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. 14 / 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^- 15 / 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. 16 / 20 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 17 / 20 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 18 / 20 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 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 20 / 20 A reaction takes place in two stages in the presence of a catalyst: Which ion is the catalyst in the reaction? Fe^2+ (aq) I^– (aq) SO4^2– (aq) S2O8^2– (aq) The catalyst must remain unchanged at the end of the reaction. Your score isThe average score is 85% 0% Restart quiz
