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Seminar form 4= revision on intro to chemistry, structure of atoms, formulae and chemical equation with answers
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Seminar form 4= revision on intro to chemistry, structure of atoms, formulae and chemical equation with answers

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basic concepts in chemistry

basic concepts in chemistry

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  • 1.  
  • 2. CHEMISTRY FORM 4 PREPARATION FOR STANDARDIZED TEST
  • 3. QUESTION 1: An experiment is conducted to investigate the effect of temperature on the rate of reaction. 5 set of 50cm 3 of 1.0 mol dm -3 sulphuric acid is reacted with 5g of magnesium ribbon at a different temperature.
  • 4. DOES THE TEMPERATURE AFFECT THE RATE OF REACTION BETWEEN SULPHURIC ACID AND MAGNESIUM RIBBON?
      • a) State a problem statement for above experiment. [2 m ]
  • 5.
      • b) Identify all the variables in this experiment.
        • i) Manipulated variable
        • ii) Responding variable
        • iii) Controlled variable
    TEMPERATURE OF ACID RATE OF REACTION
        • CONCENTRATION AND VOLUME OF ACID, MASS OF MAGNESIUM RIBBON
  • 6.
      • c) State one suitable hypothesis for this experiment.
    THE HIGHER THE TEMPERATURE , THE HIGHER THE RATE OF REACTION BETWEEN SULPHURIC ACID AND MAGNESIUM RIBBON.
  • 7. QUESTION 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.
  • 8. Time (min) 0 ½ 1 1½ 2 2½ 3 3½ Temp. ( o C) 60.0 64.0 68.0 72.0 76.0 80.0 80.0 80.0 Time (min) 4 4 ½ 5 5½ 6 6½ 7 7½ Temp. ( o C) 80.0 80.0 80.0 80.0 80.0 83.0 86.0 89.0
  • 9. a) Draw a graph of the temperature against time for the experiment and locate the melting point for substance Y [4 m]
  • 10.  
  • 11. b) Explain why there is no change in temperature from min 2½ to 6 min HEAT ABSORB BY THE PARTICLES IS USE TO OVERCOME THE ATTRACTIVE FORCES BETWEEN THE PARTICLES
  • 12. c) Draw the arrangement of particles at 2 minutes of heating. [1m]
  • 13. QUESTION 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
  • 14.
    • Based on information given in Table 3, answer the following questions.
      • a) What is meant by nucleon number? [1 m]
    TOTAL NUMBER OF PROTON AND NEUTRON IN THE NUCLEUS OF AN ATOM
  • 15.
      • b) What is the number of neutron for particle W ? [1 m]
    1
      • c) Write the electron arrangement for atom: [1 m]
    V : 1 Z: 2.8.8.2
  • 16.
      • d) Draw the structure of atom X [1 m]
  • 17. e) Which of the above atoms are isotopes? Explain your answer. [2 m] V AND W. BOTH ATOMS HAVE SAME PROTON NUMBER BUT DIFFERENT NUCLEON NUMBER OR V AND W. BOTH ATOMS HAVE SAME NUMBER OF PROTON BUT DIFFERENT NUMBER OF NEUTRON
  • 18.
      • f) How many valence electrons in atom X? [1 m]
    Electron arrangement: 2.1 Therefore; valence electron = 1
  • 19. Seminar form four= revision for selaras 1- april 2011
  • 20.
    • 4) An experiment was conducted in order to determine the empirical formula of magnesium oxide.
      • a) Give the meaning of empirical formula.
    IS THE FORMULA THAT GIVES THE SIMPLEST WHOLE NUMBER RATIO OF ATOM OF EACH ELEMENT IN A COMPOUND
  • 21.
      • Why must the magnesium ribbon be cleaned with sandpaper?
    •  
      • Why does the crucible need to be covered with its lid as soon as the magnesium start burning?
    TO REMOVE THE OXIDE LAYER TO PREVENT THE WHITE FUMES FROM ESCAPING
  • 22.
        • i) Calculate the mass of mg used.
    MASS OF Mg = (24.70-22.30) = 2.4 g d) Description Mass, g Mass of crucible + lid 22.30 Mass of crucible + lid + magnesium 24.70 Mass of crucible + lid + magnesium oxide 26.30
  • 23.
        • ii) Calculate the mass of oxygen that reacts with magnesium.
    • iii) Calculate the number of moles of magnesium used.
    MASS OF OXYGEN = 26.30-24.70 = 1.6 MOLE OF MAGNESIUM = 2.4 / 24 = 0.1
  • 24.
        • iv) Calculate the number of moles of oxygen that has reacted.
    MOLE OF OXYGEN = 1.6/16 = 0.1
        • v) Determine the empirical formula of magnesium oxide.
    Mg: O 0.1 : 0.1 1 : 1 MgO
  • 25.  
  • 26.
    • The reaction between hydrochloric acid and zinc carbonate was written below. hydrochloric acid + zinc carbonate  zinc chloride + carbon dioxide + water
    • a) Write the chemical formula for zinc chloride.  
  • 27. Rewrite the equation above as chemical equation. [2 m] hydrochloric acid + zinc carbonate  zinc chloride + carbon dioxide + water HCl + 2 ZnCO 3  ZnCl 2 + CO 2 + H 2 O
  • 28. If 12.5 g of zinc carbonate react completely in the reaction above calculate, i) the number of mole of hydrochloric acid being used? [3m]
  • 29. 2HCl + ZnCO 3  ZnCl 2 + CO 2 + H 2 O
  • 30. ii) the mass of zinc chloride obtained. 2HCl + ZnCO 3  ZnCl 2 + CO 2 + H 2 O
  • 31. iii) the vol of gas collected at room temp 2HCl + ZnCO 3  ZnCl 2 + CO 2 + H 2 O