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. 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 3. 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% 4 / 20 4. 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 5 / 20 5. An element T forms an ion, T2+, which has an electronic arrangement 2.8.8. Which statement(s) concerning T is/are correct? I T is an alkali metal. II T forms a basic oxide with oxygen. III T is in Period 4 of the Periodic Table. I and II only I and III only II and III only I , II and III Since its ion's charge is 2+, it is in group 2 and called Alkali Earth metal not alkali metal. 2,8,8,2 is calcium which is in period 4 as its atom have 4 electron shells. Its oxide is basic. 6 / 20 6. 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 7 / 20 7. 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 8 / 20 8. 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 9 / 20 9. 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 10 / 20 10. 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 11 / 20 11. 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^- 12 / 20 12. 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 13 / 20 13. 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. 14 / 20 14. Which of these Group 1 elements reacts most violently with water? caesium lithium potassium rubidium reactivity increases as it goes down the group. 15 / 20 15. 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. 16 / 20 16. 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 17 / 20 17. 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. 18 / 20 18. 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 19. 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 20 / 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
