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Questions and answers on diagram part 2 sabtu 5nov=galas day

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  • 1. hydrophilichydrophobic Hydrophilic: Dissolve in water Hydrophobic: Dissolve in grease
  • 2. c) State 2 advantages of soap over detergents d) How does soap cleanse grease? -Biodegradable - do not harm aquatic life -Soap dissolves in water and lowers surface tension of water making the clothes wet -The hydrophibic part dissolve in grease, the hydrophilic part dissolve in water -Movement of water helps to loosen the grease into small droplets
  • 3. -The droplets do not coagulate due to the repulsion between the negative charges on their surface. -Rinsing washes away these droplets and leave the surface clean 7) State 2 advantages of detergents -Effective in hard water and soft water - effective in acidic water
  • 4. 8) Why does bronze harder than copper? The presence of tin atoms disturb the orderly arrangement of copper atoms. When force is given, the layers of atoms do not slide easily
  • 5. 9) Heating copper(II) carbonate a)Write the chemical equation b) State 2 observations c) If copper(II) nitrate is heated, the chem. equation -limewater becomes milky -black powder formed 23 COCuOCuCO +→ 2223 42)(2 ONOCuONOCu ++→
  • 6. 10) Heating of naphthalene a)Melting point of naphthalene b)What is the function of bath tub? c)What precautions to be taken to obtain a good graph? Give uniform heating for naphthalene 80o C Naphthalene must be stirred continously during heating
  • 7. 11) To determine heat of combustion of methanol a)State 3 precaution to obtain a good reading? -water in copper can must be stirred continously -the spirit lamp must be closed immediately with cap after heating to avoid hot alcohol from evaporating - Wooden block must be used to make sure the wick touch the bottom of copper can
  • 8. 12) To determine the empirical formula of copper(II) oxide a)Chemical equation a)State 2 precautions -Hydrogen gas must be allowed to pass through combustion tube for a few minutes before CuO is heated -Flow of hydrogen gas must be continued throughout heating OHCuHCuO 22 +→+
  • 9. To determine the empirical formula magnesium oxide Chemical equation State 2 precautions agnesium ribbon must be cleaned using andpaper e crucible lid must be open from time to me to allow oxygen react with agnesium MgOOMg 22 2 →+
  • 10. Electrolysis of copper(II) sulphate soltn Half equation at cathode Half equation at anode Observation at cathode own solid deposited Observation at anode ervescence occur eOHOOH CueCu 424 2 22 2 ++→ →+ − +
  • 11. Simple voltaic cell Half equation at –ve electrode half equation at +ve electrode Observation at –ve electrode agnesium electrode becomes thinner Observation at +ve electrode ervescence occur 2 2 22 2 HeH eMgMg →+ +→ + +
  • 12. Experiment to show transfer of electron a distance Half equation at +ve electrode half equation at -ve electrode Observation at +ve electrode own solution turns to colourless observation at -ve electrode our changes from colourless to brown eII BreBr 22 22 2 2 +→ →+ − −
  • 13. Preparation of soap in laboratory Name of reaction: Saponification What is the function of concentrated alkali? To hydrolyse the oil Observation: hite precipitate that formed foam when aken with water Salt is added to the mixture during exp. Why? precipitated the soap produced
  • 14. ) Energy level diagram for an exothermic action 4 informations can be obtained: 1 mole of NaOH react with 1 mole HCl to rmed 1 mole of NaCl and 1 mole of H2O Energy level for reactant is higher than nergy level for product An exothermic reaction Heat of reaction = -54kJmol-1
  • 15. Relationship between: Volume of gas against time te of reaction decreases with time oncentration of sodium thiosulphate against time hen the concentration of sodium osulphate increases, the shorter the me taken for reaction to occur
  • 16. iii)Concentration of sodium thiosulphate against 1/time Concentration of sodium thiosulphate is directly proportional to 1/time iv) Temperature of solution against time When temperature of solution increases, the shorter time taken for reaction to occur v) Temperature of solution against 1/time Temperature of solution increased proportionally with 1/time

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