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# Revison chapter 3

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• 1. 1 REVISION Chemical formulae and equationName…………………………………………………….class…………………..date…………………..1) Relative atomic mass of magnesium is 24. Explain this statement in terms of i) Hydrogen standard …………………………………………………………………… ii) Carbon-12 standard………………………………………………………………2) If an atom W is 32 times heavier than 1/12 of the mass of 1 atom carbon -12, what is its relative atomic mass? …………………………………………………………………………………………….3) An atom of metal M is 1.6 times heavier than an atom of calcium. What is the relative atomic mass of M? ( Ca=40) ………………………………………………………………………………………………….4) How many times a lead atom is heavier than a carbon atom? ( Pb= 207, C=12)………… …………..5) A compound has the formula of NaXO3. The relative molecular mass is 151. Find the relative atomic mass of X(given RAM of Na, 23: O,16) ……………………………………………………………………………………………………..
• 2. 26) What is meant by empirical formula and molecular formula? ………………………………………………………………………………. ………………………………………………………………………………………………………… ……………………………………………. ………………………………………………………………………………………………………… …………………………………………………………………………………….….7) Determine the empirical formula for substance belowsubstance Molecular Empirical substance Molecular Empirical formula formula formula formula a) benzene C6H6 b) Glucose C6H12O6 c) Propene C3H6 d) ammonia NH38) Metal X combines with 4.32 g of oxygen to form 13.68 g of metal oxide X. What is the empirical formula of the metal oxide? given RAM O is 16 ………………………………………………………………………………………………9) The empirical formula of a compound is CH2. If its molecular formula is 56, what is its molecular formula? ………………………………………………………………………………………………………10) A compound contain 40% carbon, 53.3 % oxygen ,and the rest is hydrogen If the molar mass of the compound is 180, find i) Empirical formula
• 3. 3 …………………………………………………………………………………………. ii) Molecular formula ……………………………………………………………………………………………11) Complete the formula below Mole = mass/ Mole = volume of gas / Mole = number of particles/ CuCO3 6.2 gram +12) CuO CO2 From the reaction above, calculate ( given RAM of Cu,64: C,12: O,16) a) Mole of copper carbonate used ……………………………………………… b) Mass of copper oxide formed ……………………………………………….. c) Volume of carbon dioxide released ………………………………………………… d) Number of molecules of carbon dioxide released …………………………………….. e) Number of atoms of carbon dioxide released ……………………………………………
• 4. 413) An experiment was conducted in order to determine the empirical formula of magnesium oxide. (a) Draw diagram for the experiment ……………………………………………………………………………………… [2m] b) Give the meaning of empirical formula. [1 m] ………………………………………………………………………………………………. c) Why must the magnesium ribbon be cleaned with sandpaper before the experiment? …………………………………………………………………………………………….. d) Why the crucible need to be covered with its lid as soon as the magnesium start burning? [1 m] …………………………………………………………………………………………. e) The results of the experiment are as follows: Description Mass, g Mass of crucible + lid 22.30 Mass of crucible + lid + magnesium 24.70 Mass of crucible + lid + magnesium oxide 26.30 [relative atomic mass: O,16 ; Mg,24] Based on the above result, i) Calculate the number of moles of magnesium used. [1 m] …………………………………………………………………………….. ii) Calculate the number of moles of oxygen that has reacted. [1 m] ………………………………………………………………………………. iii) Determine the empirical formula of magnesium oxide. [1 m]
• 5. 5 ………………………………………………………………………………5. The reaction between hydrochloric acid and zinc carbonate was written below. hydrochloric acid + zinc carbonate → zinc chloride + carbon dioxide + water a) Rewrite the equation above as chemical equation. [2 m] ____________________________________________________ b) If 12.5 g of zinc carbonate react completely in the reaction above calculate, [given molar mass calcium carbonate = 125 g/mol, relative atomic mass: Zn,65; C,12;O,16;H,1;Cl,35.5; molar volume of gas at room temperature: 24dm3/mol] i) the number of mole of hydrochloric acid being used? [3m] …………………………………………………………………………………………. ii) the mass of zinc chloride obtained. [2m] ………………………………………………………………………………………… iii) the volume of gas collected at room temperature. [2m] ………………………………………………………………………………………….. iv)Number of molecules of carbon dioxide released [2m] ………………………………………………………………………………………….
• 6. 6END