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Heat of precipitation
In an experiment to determine the heat of precipitation of silver nitrate,
50 cm^{3} of 1.0 mol dm^{3} hydrochloric acid is added to 50 cm^{3} of 1.0 mol dm^{3} silver nitrate solution.
The following results are obtained.
Initial temperature of silver nitrate solution (^{o}C)

28.0

Initial temperature of hydrochloric acid solution (^{o}C)

29.0

Highest temperature of the mixture (^{o}C)

35.5

Calculate the heat of precipitation of silver chloride, AgCl
[Specific heat capacity of water is 4.2 J g^{1} ^{o}C^{1} and density of water is 1 g cm^{3}]
(ans:  58.8 kJ mol^{1})
Heat of precipitation (Find the heat change)
Calculate the heat change when 200 cm^{3} of 0.5 mol dm^{3} calcium chloride, CaCl_{2 }solution is added to 200 cm^{3} of 0.5 mol dm^{3} sodium carbonate, Na_{2}CO_{3} solution if the heat of precipitation of calcium carbonate, CaCO_{3} is +12.6 kJ mol^{1}
[ Specific heat capacity of solution : 4.2 J g^{1 0}C^{1} . Density of solution : 1 g cm^{3} ]
(ans: 1.26 kJ)
Heat of displacement (Calculation)
To determine the heat of displacement of copper from a copper (ll) sulphate solution by zinc.
Procedure :
1. Measure 25 cm^{3} 0.2 mol dm^{3} copper(ll) sulphate solution and pour into a polystyrene cup.
2. Put the thermometer into the copper(ll) sulphate solution. Record the initial temperature,
3. Add half a spatula of zinc powder (in excess) quickly into copper(ll) sulphate solution.
5. Stir the mixture with the thermometer and record the highest temperature achieved.
Result :
Initial temperature of copper(II) sulphate solution = 30.0 ^{0}C
Highest temperature of the mixture = 40.0 ^{0}C
Calculate the heat of displacement of copper from a copper (ll) sulphate solution by zinc.
[ Specific heat capacity of solution : 4.2 J g^{1 0}C^{1} . Density of solution : 1 g cm^{3} ]
(Ans:  210 kJ mol^{1})
Heat of displacement (Find the change of temperature)
In an experiment, excess magnesium powder is added to 50 cm^{3} of 0.25 mol dm^{3 }
iron(ll) sulphate solution. The thermochemical equation is shown below,^{}
Mg(s) + Fe^{2+} (aq) à Mg^{2+} (aq) + Fe (s) ΔH = 80.6 kJ mol ^{ 1}
What is the change in temperature?
[ Specific heat capacity of solution : 4.2 J g^{1 0}C^{1} . Density of solution : 1 g cm^{3} ]
(ans: 4.8 ^{o}C)
Heat of neutralisation (Calculation)
To determine the heat of neutralization between a strong acid (hydrochloric acid) and a strong alkali (sodium hydroxide)
Procedure :
1. Measure 50 cm^{3} 2.0 mol dm^{3 }sodium hydroxide solution and pour it into the polystyrene cup,^{}
2. Put the thermometer into the sodium hydroxide solution. Record the initial temperature,
3. Measure 50 cm^{3} 2.0 mol dm^{3 }hydrochloric acid solution and record the initial temperature,
4. Pour the hydrochloric acid solution quickly into the sodium hydroxide solution in the
polystyrene cup.
5. Stir the mixture with the thermometer and record the highest temperature achieved.
Result :
Initial temperature of sodium hydroxide solution = 29.0 ^{0}C
Initial temperature of hydrochloric acid solution = 29.0 ^{0}C
Highest temperature of the mixture = 42.0 ^{0}C
[ Specific heat capacity of solution : 4.2 J g^{1 0}C^{1} . Density of solution : 1 g cm^{3} ]
Calculate the heat of neutralization.
(Ans:  54.6 kJ mol^{1})
Electrolysis (Types of electrodes)
III) Types of electrodes used Electrolysis of 0.2 mol dm^{3} copper(II) sulphate solution Using copper electrodes Ions present:  
Electrode  Anode (+)  Cathode () 
Ions attracted  
Ion discharged  
Half Equation  
Observation  
Product formed    
Colour of the electrolyte 
Electrolysis of 1.0 mol dm3 sodium chloride solution
II) The concentration of ions in the solution Electrolysis of 1.0 mol dm^{3} sodium chloride solution Ions present:  
Electrode  Anode (+)  Cathode () 
Ions moving  
Ion discharged  
Reason  
Half Equation  
Observation  
Product formed 
Electrolysis of Aqueous solutions
1. Example, sodium chloride solution consists of 4 type of ions
Ions  Cation  Anion 
Sodium chloride  Na^{+}  Cl^{} 
Water  H^{+} 
2. Three factors that affect the selective discharge of ions at the
electrodes during electrolysis of an aqueous solution:
I The position of ions in the electrochemical series.
II The concentration of ions in the solution
III Types of electrodes used
Observation  inference 
Colourless gas released  H_{2} / O_{2} 
Greenish yellow gas (Blue litmus → red → white)  Cl_{2} 
Brown gas  Br_{2} 
Grey solid deposited  Pb/Al 
Brown solid deposited  Cu 
Electrolysis (molten)
Electrolysis of molten lead(II) bromide Ion present:  
Electrode  Anode (+)  Cathode () 
Ions moving  
Half Equation  
Observation  
Product formed 
Answer:
Reactivity of Group 1 elements
When going down Group 1, the alkali metals become more reactive when react with water
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