SPM 2011 TimeTable

The SPM 2011 Timetable 

Form 5 Chapter 4 Thermochemistry

Describe an experiment to determine the heat of precipitation of silver chloride

Diagram:

Apparatus:

Measuring cylinders, thermometer and plastic cup

Materials:

0.5 mol dm^-3 silver nitrate solution, 0.5 mol dm^-3 sodium chloride solution

Procedure:
1.      25cm3 of 0.5 mol dm-3 sodium chloride solution is measured and poured into a clean and dry plastic cup using a measuring cylinder. 2.      The initial temperature of sodium chloride solution is measured and then recorded. 3.      Using another measuring cylinder, 25 cm3 of 0.5 mol dm-3 silver nitrate solution is measured. The initial temperature of the silver nitrate solution is measured after 5 minutes and recorded. 4.      The silver nitrate solution is poured quickly and carefully into the sodium chloride solution. 5.      The mixture is stirred with a thermometer throughout the experiment and the highest temperature obtained is recorded.
Result:
Mass, m	c	q
= (25 + 25) g = 50 g	4.2	Initial temperature of sodium chloride solution     = T1oC Initial temperature of the silver nitrate            = T2 oC Highest temperature reached                                            = T4 oC => Average initial temperature = (T1+T2)/2                       = T3 oC è Increase in temperature,  q = (T4 - T3) oC
Calculation:
No of moles of sodium chloride used		No of moles of silver nitrate used
= MV/1000 = 0.0125 mole		= MV/1000= 0.0125 mole
Chemical equation: AgNO3 (aq) + NaCl (aq) à AgCl (s) + NaNO3 (aq) Ionic equation:              Ag + (aq)                              +              Cl- (aq) à           AgCl (s)                                                              1 mole                                  1 mole                  1 mole Heat released =              mcq                                              =              (25 + 25 ) x 4.2 x (T4 - T3)                                              =              x J 0.0125 mole of AgCl precipitated releases x J of heat energy. Therefore, 1 mole of AgCl precipitated will released Heat of precipitation, DH = x/0.0125 J = y J Thermochemical equation: AgNO3 (aq) + NaCl (aq) à AgCl (s) + NaNO3 (aq)                             DH = - y/1000 kJmol-1

Form 5 Chapter 4 Thermochemistry

Planning of experiment:

1		Different members of this homologous series have different heat of combustion. Table below shows the heat of combustion of some alcohols.
		Alcohol Alcohol Heat if combustion (KJ mol-1) Haba pembakaran (KJ mol-1) Methanol Metanol - 728 Ethanol Etanol - 1376 Propan-1-ol Propan-1-ol -2016 Butan-1-ol Butan-1-ol - 2678
		Plan a laboratory experiment to determine the heat of combustion of alcohols shown in the table. Your planning should include the following aspects:
		(a)                Statement of the problem Pernyataan masalah  (b)              All the variables Semua pembolehubah                        (c)               Hypothesis             Hipotesis                                 (d)              List of materials and apparatus Senarai bahan dan radas (e)               Procedure             Prosedur                                 (f)                Tabulation of data Penjadualan data                   [17 marks] [17 markah] Suggested Answer: Aim To study the heat of combustion of different alcohols . Problem statement Do alcohols with more carbon atoms per molecule have higher value of heat of combustion? Variables MV: Different types of alcohol RV: Heat of combustion FV:   1. Volume of water        2. type of container/size of container Hypothesis Different type of alcohol produces different heat of combustion. Apparatus & Materials A: copper beaker, spirit lamp, thermometer, weighing balance, wooden block, tripod stand, wind shield, measuring cylinder. M: Ethonol, propanol, butanol, water, Procedure: 1. [200 cm3] of water is poured into a [copper] beaker. 2. Initial temperature of the water is recorded. 3. A spirit lamp is half filled with ethanol. 4. Initial mass of the spirit lamp is recorded. 5. Put the spirit lamp under the copper beaker and ignite the wick immediately. 6. Stir the water and the flame is put off after the temperature has increased by 30oC. 7. The highest temperature of the water is recorded. 8. Immediately the final mass of the spirit lamp is recorded. 9. Repeat the experiment by replacing ethanol with propanol and butanol. Tabulation of data Type of alcohol Initial temperature / oC Final temperature / oC Initial mass of spirit lamp / g Final mass of spirit lamp / g Methanol Ethanol Propan-1-ol Butan – 1- ol

Sample of Essay Question

Form 4 Chapter 5:

1		Table 11 shows the proton number of atoms P, Q and R.
		Element P Q R Proton number 8 12 17
	a)	Based on electron arrangement, explain the formation of chemical bond between
	i)	element P and element P                                                      [5 marks ]
	ii)	element Q and element R                                                     [7 marks ]
	b)	Gas P reacts with element Q to produce a white solid.
	i)	Write a chemical equation for the reaction between gas P and element Q.
	ii)	State three physical properties of the white solid.              [ 4 marks] ]
	c)	What is the position of element Q in the Periodic Table of the elements? Explain how you obtain your answer.                                  [ 4 marks ]

Suggested Answer:

1	a)i	1.   Two atoms of P combine through covalent bond.                            2.   Each atom of P needs two more electrons to achieve octet electron arrangement. 3.   Each atom of P contributes two electrons to each other for sharing.               4.   Two atoms of P share two pairs of electrons. 5.   A double covalent bond is formed.
	ii)	1.    Atom Q and atom R combine through ionic bond 2.    To achieve octet electron arrangement,                                          3.    atom Q with 6 valence electrons loses two electrons to form Q2+ ion              4.    Two atom R, each atom with 7 valence electrons gain one electron to form R- ion.                                                                       5.   Q2+ ion and R- ion are attracted to each other by strong electrostatic force.1   Diagram
	b)i	2Q   +   P2      -->       2QP
	ii)	Have high melting point Usually soluble in water                                                                            Conduct electricity in the molten state or aqueous solution.
	c)	1.    Element Q is located in Group 2                                                       2.    because it has two valence electrons                                            3.    Element Q is located in Period 3                                                       4.    because it has three shells occupied with electrons

Describe of experiment in Paper 2 (Essay)

	Form 4: Chapter 3:  Describe an experiment in the laboratory to determine the empirical formula of magnesium oxide. Your answer should consist of the following.
	Procedures of the experiment Calculation involved Precautions need to be taken Given that relative atomic mass of Mg = 24,   O = 16             [13 marks]

Suggested Answer:

[Material and apparatus ]

[Magnesium ribbon, sand paper, crucible with lid, tongs, Bunsen burner, tripod stand, pipe-clay triangle and balamce.] or  [diagram]  2    

[Procedure]

·          A crucible and its lid is weighed and its weight is recorded.        1

·          A 10 cm length of magnesium ribbon is coiled loosely and is placed in the crucible.                                                        1

·          The crucible with its lid and content are weighed again and the weight is recorded.                                                                   1

·          The crucible is heated strongly without its lid.                             1

·          When the magnesium starts to burn, the crucible is covered with its lid.   1

·          Using a pair of tongs, the lid is lifted at intervals.                          1

·          When the burning is completed, the lid is removed and
the crucible is heated strongly for 2 minutes.                               1

·          The rucible is allowed to cool to room temperature.                     1

·          The crucible and its lid and content are weighed again and its weight is recorded.                                                                        1

                                                                                                            max 5

[Precautions taken]                         

·          The magnesium ribbon is cleaned with sand paper to remove the layer of magnesium oxide on the surface.

·          The crucible must cover with its lid to prevent the white fumes of magnesium oxide of escaping.            

·          The processes of heating, cooling and weighing are repeated until a constant mass is obtained.                              [any two of the above]                              2

[ Results ]                                                                        

Crucible + lid                                          =   a  g         

Crucible + lid +  magnesium                    =   b  g         

Crucible + lid +  magnesium oxide          =   c  g                     1

[ Calculation ]                                                                    

Element	Magnesium	Oxygen
Mass(g)	b-a	c-b
Number of moles of atoms	b-a/24	c-b/16
Simplest ratio of moles	X	y

Empirical formula =  Mg_xO_y                                                       2+1