O Levels Combined Chemistry G3 O Levels G3 Combined Chemistry Paper 1 mock Name 1 / 20 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. 2 / 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 3 / 20 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 4 / 20 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 5 / 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 6 / 20 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. 7 / 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. 8 / 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, 9 / 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 10 / 20 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. 11 / 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% 12 / 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 13 / 20 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% 14 / 20 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. 15 / 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. 16 / 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 17 / 20 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. 18 / 20 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 % 19 / 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. 20 / 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 Your score isThe average score is 85% 0% Restart quiz
