CHEMISTRY                     FORM 4 – PREPARATION FOR STANDARDIZED TEST1) An experiment is conducted to investigate the e...
__________________________________________________________     (c) Draw the arrangement of particles at 2 minutes of heati...
____________________________________________________________     f) How many valence electrons in atom X?                 ...
hydrochloric acid +      zinc carbonate → zinc chloride + carbon dioxide + water   a.      Write the chemical formula for ...
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Seminar revision on chapter intro to chemistry, structure of atom, chemical formula and equations

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Seminar revision on chapter intro to chemistry, structure of atom, chemical formula and equations

  1. 1. CHEMISTRY FORM 4 – PREPARATION FOR STANDARDIZED TEST1) An experiment is conducted to investigate the effect of temperature on the rate of reaction. 5 set of 50cm3 of 1.0 mol dm-3 sulphuric acid is reacted with 5g of magnesium ribbon at a different temperature. a) State a problem statement for above experiment. [2 m ] ______________________________________________________________ b) Identify all the variables in this experiment. [3m] i) Manipulated variable :______________________________________ ii) Responding variable : ______________________________________ iii) Controlled variable : ______________________________________ c) State one suitable hypothesis for this experiment. [2 m ] ___________________________________________________________2) A group of students has carried out an experiment to determine the melting point of substance Y. A boiling tube contained substance Y solid is heated in a water bath. The temperature of substance Y is recorded every 30 seconds. The result is as shown in table 2 below.Time 0 ½ 1 1½ 2 2½ 3 3½ 4 4½(min)Temperature 60.0 64.0 68.0 72.0 76.0 80.0 80.0 80.0 80.0 80.0(o C)Time 5 5½ 6 6½ 7 7½(min)Temperature 80.0 80.0 80.0 83.0 86.0 89.0(o C) Table 2 (a) Draw a graph of the temperature against time for the experiment and locate the melting point for substance Y [4 m] (b) Explain why there is no change in temperature from min 2½ to 6 min.[2m] 1
  2. 2. __________________________________________________________ (c) Draw the arrangement of particles at 2 minutes of heating. [1m]3. Table 3 shows the proton number and nucleon number for atom V, W, X, Y and Z. Atom Proton number Nucleon number V 1 1 W 1 2 X 3 7 Y 6 12 Z 20 40 Table 3 Based on information given in Table 3, answer the following questions. a) What is meant by nucleon number? [1 m] _________________________________________________________ b) What is the number of neutron for particle W ? [1 m] _________________________________________________________ c) Write the electron arrangement for atom [1 m] V : _____________________ Z : _____________________ d) Draw the structure of atom X [1 m] e) Which of the above atoms are isotopes? Explain your answer. [2 m] 2
  3. 3. ____________________________________________________________ f) How many valence electrons in atom X? [1 m] ___________________________________________________________4. An experiment was conducted in order to determine the empirical formula of magnesium oxide. a) Give the meaning of empirical formula. [1 m] ___________________________________________________________ b) Why must the magnesium ribbon be cleaned with sandpaper? [1 m] ___________________________________________________________ c) Why the crucible need to be covered with its lid as soon as the magnesium start burning? [1 m] ___________________________________________________________ d) 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 mass of magnesium used. [1 m] ii) Calculate the mass of oxygen that reacts with magnesium. [1 m] iii) Calculate the number of moles of magnesium used. [1 m] iv) Calculate the number of moles of oxygen that has reacted. [1 m] v) Determine the empirical formula of magnesium oxide. [1 m]5. The reaction between hydrochloric acid and zinc carbonate was written below. 3
  4. 4. hydrochloric acid + zinc carbonate → zinc chloride + carbon dioxide + water a. Write the chemical formula for zinc chloride. [1 m] ____________________________________________________ b. Rewrite the equation above as chemical equation. [2 m] ____________________________________________________ c. 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] 4

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