O Levels Combined Chemistry G3 O Levels G3 Combined Chemistry Paper 1 mock Name 1 / 20 1. 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. 2 / 20 2. 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 3 / 20 3. Elements X and Y combine to form an ionic compound. Atoms of X have more protons than atoms of Y. Atoms of Y have more valence electrons than atoms of X. Which statement is correct? Ions of X are negatively charged. Atoms of X have more electron shells than atoms of Y. X and Y are in the same period of the Periodic Table. X and Y are in the same group of the Periodic Table. X and Y, one is metal, one is non-metal. since Y has more valence then X is metal and Y is non-metal and X has more electron shell since it has protons. 4 / 20 4. 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. 5 / 20 5. 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^- 6 / 20 6. 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, 7 / 20 7. 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. 8 / 20 8. 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 9 / 20 9. 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 10 / 20 10. 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 11 / 20 11. 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. 12 / 20 12. In which chemical reaction does the named product have a higher relative molecular mass than the reactant? the formation of ethanol from glucose the formation of propene from octane the formation of carbon dioxide from butane the formation of dichloromethane from methane methane CH4 molar mass = 12 +4 = 16g dichloromethan CH2Cl2 molar mass = 12 +2 + 71 = 85g 13 / 20 13. 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 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. 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. 16 / 20 16. 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. 17 / 20 17. 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 18 / 20 18. 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% 19 / 20 19. Which of these Group 1 elements reacts most violently with water? caesium lithium potassium rubidium reactivity increases as it goes down the group. 20 / 20 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 Your score isThe average score is 85% 0% Restart quiz
