STPM CHEMISTRY 962/2

STPM Semester 2 2014 Timetable

FORECAST QUESTION

CHEMISTRY STPM 962/2

1. When one mole of sodium bromide dissolves in water, the enthalpy change is -8 kJ mol^-1. If the lattice energy of sodium bromide and the hydration energy of the Na⁺ ion are -736 kJ mol^-1 and -406 mol^-1 respectively, what is the hydration energy of the Br^- ion?                                                                                                                               

A   -1150 kJ mol^-1            B             -338 kJ mol^-1        C      -322 kJ mol^-1        D          +1 150 kJ mol^-1

2. Which of the following is not required in the calculation of the lattice energy of calcium oxide sing Born Haber cycle ?

A. Enthalpy of  hydration    B. Enthalpy of ionization        C. Enthalpy of atomization          D. Electron affinity

3. The standard enthalpy of formation of ethanol is -278 kJ per mole. Which equation relates to the formation of ethanol under standard conditions?                                                                                                                          

A.       2C(g) + 3H₂(g)  + 1/2O₂ (g) à C₂H₅OH(l)

B.       2C(s) + 3H₂(g)  + 1/2O₂ (g)  à C₂H₅OH(l)

C.      2C(g) + 3H₂(g)  + 1/2O₂ (g) à C₂H₅OH(l)

D.      4C(g) + 6H₂(g)  + O₂ (g)     à 2C₂H₅OH(l)

4.  Which of the following is not a disproportionation reaction ?                                                                 

A.       Cl₂ + NaOH à NaOCl + NaCl +H2O

B.       3Cl₂ + 6NaOH à NaClO₃ +  5NaCl  + 3H₂O

C.      4HCl + MnO₂ à Cl₂ + MnCl₂ + 2H₂0

D.      3NaOCl à NaClO₃ + 3 NaCl

5. The relationship between electrode potential and ion concentration is given by the following Nernst equation.

For the reaction Co(s) + Ni²⁺ (aq)à  Co²⁺⁽aq) + Ni(s), the E value is +0.0300 V.   If the concentration of Co²⁺ is reduced to 0.1000 mol dm^-3 and the concentration of Ni²⁺ is maintained, what is the value of E^q   for the cell under the same conditions?

A-0.0292 V            B+0.0004 V             C           +0.0596 V                         D   +0.0892 V                               

6. The graphs below show the variation in three physical properties of elements in Period 3 of the Periodic Table

What are the physical properties that the graphs refer to?                                                                        

I                       II                                      III

A Boiling point      Conductivity          Vaporisation enthalpy

B Melting point     Atomic radius       First ionization energy

C Melting point     Conductivity          First ionization energy

D Conductivity      Atomic radius       First ionization energy

7. . The successive ionization energies, in kJ mol^-1 , of an element in the Periodic Table are given below.

940 (First), 2080, 3090, 4140, 7030, 7870, 16 000, 19 500

In which group in the Periodic Table is this element likely to be located?                                                                              

A   Group 13         B    Group 14        C    Group 15        D    Group 16      

8.   The carbonates of the Group 2 elements (beryllium to barium) decompose according to the equation

MCO₃(s)→MO(s) + CO₂(g).

Which of the following combinations is correct when descending Group 2?                                                         

Lattice energy of MCO₃      Lattice energy of MO          Decomposition temperature of MCO₃

A Increases                           Increases                              Increases

B Increases                           Decreases                            Increases

C Decreases                        Increases                              Increases

D Decreases                        Decreases                            Increases

9. Which statement best explains why the thermal stability of the carbonates of Group 2 metals of the Periodic Table increases going down the group?                                                                                                                                                           

A The polarization power of the metal ion towards the CO₃^2- ion decreases

B The strength of ionic bond in the metal carbonate increases

C The radius of the metal ion increases.

D The electronegativity of the metal decreases

10. Which tetrachloride can bleach the colour of litmus paper at room temperature?                                         

A SiCl₄                                B GeCl₄                                 C SnCl₄ D                                    D PbCl₄

11. The diagram below shows the structure of a type of silicate.                                                                              

Which of the following statements is correct with regard to the above structure?

A    It represents the structure of asbestos.

B    The repeating unit is SiO₄^4-

C    The structure is found in the mineral pyroxene.

D    The ratio of Si to O is 1 : 4.

12.  The reactivity of the halogens Cl₂, Br₂ and I₂ decreases down Group 17 of the Periodic Table. Which property does not influence the trend in the reactivity of the halogens?                                                                                                          

A Atomic size                        B Electron affinity                 C Ionization energy             D Bond energy

13.  Most of the transition elements and their compounds are heterogeneous catalysts which are useful for various reactions. The transition elements possess this catalytic power because they ……                                                                       

A can form complexes

B can act as reducing agents

C can alter their oxidation number

D have a good adsorption characteristic

14.  The colour of a transition metal complex ion is determined by its ligand and geometry.                             

Which species has a hexadentate ligand?

A Na₂[CuCl₄]        B             [Ag(NH₃)₂]⁺           C             [Ni(EDTA)]^2-          D             [Co(C₂0₄)₃]^3-

15. The solution produced when chlorine is bubbled through dilute sodium hydroxide can be used              

A as pesticide            B as bleaching agent      C in sterilizing water               D to extract bromine

Answer:

1.       B  2. A  3. B   4. C   5. C  6. B   7. D   8. D   9. B   10. D  11.C   12.C   13. D   14. C  15. B

GOOD LUCK.......

Part A                                                                                

Time : 30 minutes

Name: _____________________________                                         Marks : ___________________________

1. In the construction of cardiac pacemakers, it is possible to use a very small magnesium electrode which creates an electrical cell with the inhaled oxygen. The relevant half-cells are as follows.

Mg²⁺  + 2e              → Mg     E⁰ = -2.38V

½ O₂ + 2H⁺ + 2e → H₂O   E⁰ = +1.23V

Under standard conditions, the cell e.m.f would be 3.61 V, but in the body a potential of 3.25 V is more usual.

What is the best explanation of this lower e.m.f ?

A The small size of the magnesium electrode

B The low concentration of Mg²⁺ ions surrounding the magnesium electrode

C The high resistance of the body fluids surrounding the electrodes.

D The pH between 7 and 8 of the body fluid surrounding the electrodes.

2. Which value would be required to estimate the lattice energy for the hypothetical ionic compound, MgH₂?

A The electron affinity of hydrogen

B The first ionization energy of hydrogen

C The magnesium-hydrogen bond energy

D The standard enthalpy change of formation of MgH₂

3. Consider the sequence of oxides given below. Which series shows an increasing order of melting point?

A Cl₂O₇, Al₂O₃, SO₃, SiO₂     B SO₃, Cl₂O₇, Al₂O₃, SiO₂                  

C SO₃, Cl₂O₇, SiO₂, Al₂O₃                D SiO₂, Al₂O₃, Cl₂O₇, SO₃

4. H₂(g)   → 2H(g)                     ∆H = +436KJ

   Br₂(g)   → 2Br(g)                    ∆H = +194KJ

   H₂(g)  +Br₂(g)   → 2HBr(g)     ∆H = -104KJ

 Use the above data to determine the ∆H for the following reaction.

  H (g) + Br(g) → HBr(g)

A -288 kJ                               B -367 kJ                         C +263 kJ                              D +526 kJ

5. The following oxides are amphoteric except

A. Al₂O₃                                 B. PbO₂                        C. SnO                                   D. SiO₂,

6. Astatine is an element in Group 17 of the Periodic Table. What are the expected properties of astatine at 25⁰ C?

	Physical state	Oxidizing power	Color
A	Solid	Weak	Black
B	Solid	Strong	Black
C	Solid	Strong	Purple
D	Liquid	Weak	Purple

7. Which of the following statements is true of glass?

A. It consists of well-arranged silicate units                                    B. It withstands the action of strong alkaline.

C. It softens at a wide range of temperatures.                                D. It can be coloured by adding soda lime

8. Compared to barium, beryllium

A. is a stronger reducing agent                                   B. forms a more basic oxide.

C. reacts more vigorously with water.                           D. form more covalent compounds

9. Which of me following block--d elements does not show general characteristics of a transition element?

A. Scandium                         B. Vanadium                         C. Copper                             D. Nickel

10. A steady current flows through an aqueous solution of potassium iodide for 4825 seconds. The iodine produced requires 12.5 cm³ of 0.80 mol dm^-3 sodium thiosulphate(VI) for complete reaction. What is the value of the current flowing in this electrolytic cell? [ I₂ ≡ 2S₂O₃ ^2- ; 1F = 96, 500 C mol^-1]

A 0.1 A                                   B 0.2 A                                   C 0.3 A                                   D 0.4 A

11. Silicon (IV) oxide is a solid whereas carbon (IV) oxide is a gas. This is because

A carbon is more electronegative than silicon

B the silicon-oxygen bond is stronger than the carbon-oxygen bond

C silicon(IV) oxide partially ionic whereas carbon(IV) oxide is purely covalent

D silicon (IV) oxide is a giant molecule whereas carbon (IV) oxide is a simple molecule

12. Chlorine gas is bubbled through aqueous sodium hydroxide. What is the use of the solution obtained?

A Deodorant                         B Antiseptic                           C Bleaching agent              D Aerosol propellant

13. The oxides of group 14 which are neutral, acidic and amphoteric are;

	Acidic	Neutral	Amphoteric
A	GeO	PbO	PbO2
B	SiO2	CO	SnO
C	CO	SiO2	GeO2
D	CO2	CO	SnO2

14. X, Y and Z are elements in the same short period of the Periodic Table. X reacts with both dilute hydrochloric acid and aqueous sodium hydroxide to form hydrogen. The oxide of Y is basic and the oxide of Z is acidic.

What is the order of increasing proton number for these elements?

A X, Y, Z                            B X, Z, Y                                C Y, X, Z                                D  Z, X, Y

15. Which graph correctly describes a trend found in the halogen group?