hydrophilichydrophobic

Hydrophilic:Dissolve in water

Hydrophobic:Dissolve in grease

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

-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

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

9) Heating copper(II) carbonatea)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

10) Heating of naphthalenea)Melting point of naphthalene

b)What is the function of bath tub?

c)What precautions to be taken to obtaina good graph?

Give uniform heating for naphthalene

80oC

Naphthalene must be stirred continously during heating

11) To determine heat of combustion of methanola)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

12) To determine the empirical formula of copper(II) oxidea)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 continuedthroughout heating

OHCuHCuO 22

13) To determine the empirical formulaOf magnesium oxidea) Chemical equation

b) State 2 precautions-magnesium ribbon must be cleaned using a sandpaper-the crucible lid must be open from time to time to allow oxygen react with magnesium

MgOOMg 22 2

14) Electrolysis of copper(II) sulphate soltna) Half equation at cathode

b) Half equation at anode

c) Observation at cathodeBrown solid deposited

Observation at anodeEffervescence occur

eOHOOH

CueCu

424

2

22

2

15) Simple voltaic cella) Half equation at –ve electrode

half equation at +ve electrode

b) Observation at –ve electrodeMagnesium electrode becomes thinner

Observation at +ve electrodeEffervescence occur

2

2

22

2

HeH

eMgMg

16) Experiment to show transfer of electron at a distancea) Half equation at +ve electrode

half equation at -ve electrode

b) Observation at +ve electrodeBrown solution turns to colourless

observation at -ve electrodeColour changes from colourless to brown

eII

BreBr

22

22

2

2

17) Preparation of soap in laboratorya) Name of reaction: Saponificationb) What is the function of concentrated

alkali? To hydrolyse the oilc) Observation: White precipitate that formed foam when shaken with water

d) Salt is added to the mixture during exp.Why?

To precipitated the soap produced

18) Energy level diagram for an exothermic reactiona) 4 informations can be obtained:- 1 mole of NaOH react with 1 mole HCl to formed 1 mole of NaCl and 1 mole of H2O- Energy level for reactant is higher than energy level for product- An exothermic reaction- Heat of reaction = -54kJmol-1

19) Relationship between:i) Volume of gas against timeRate of reaction decreases with time

ii)Concentration of sodium thiosulphateagainst time

When the concentration of sodiumthiosulphate increases, the shorter the time taken for reaction to occur

iii)Concentration of sodium thiosulphateagainst 1/time

Concentration of sodium thiosulphateis directly proportional to 1/timeiv) Temperature of solution against timeWhen temperature of solution increases,

the shorter time taken for reaction to occur

v) Temperature of solution against 1/timeTemperature of solution increased proportionally with 1/time