THE GUIDING STAR
FREE OF CHARGE SPECIAL COACHING CLASS
PRE-EXAMINATION
CHEMISTRY Time Allowed: 3 Hours
WRITE YOUR ANSERS IN THE ANSWER BOOKLET
The symbols in this paper have their usual significance
SECTION (A)
(Answer ALL questions)
1. Write TRUE or FALSE for each of the following statements. (7 marks)
(a) Alkali metals have stable electronic structures.
(b) Atomic number of an element never changes.
(c) A volume of gas expands when heated.
(d) Molarity means mol cm-3.
(e) Positive ions migrate to the anode.
(f) A reducing agent is an acceptor of electrons.
(h) Reduction is the gain of electrons.
2. Fill in the blank with the correct word(s), phrase(s), term(s), unit(s), etc., (7 marks)
as necessary.
(a) The atom without neutron is.................................
(b) Mass of a proton can be considered as.........................
(c) A volume of gas ........................... when cooled.
(d) The force acting on the unit area is the............................
(e) Nitrogen dioxide gas has a ..................... colour.
(f) ..................... is used as anode in chromium plating.
(h) An oxidizing agent is an(a).......................
3. Select the correct word(s), notation(s), term(s), unit(s), etc., given (7 marks)
in the brackets.
(a) The molecule of [NH3; ClF3; BCl3] does not deviate the octet rule.
(b) One molecule of carbon dioxide gas weighs [44g, 22g, 44 amu].
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(c) Concentrated sulphuric acid can absorb [water, oxygen, carbon dioxide].
(d) Methyl orange is yellow colour in [acid, water, alkali].
(e) Anion is oxidized at the [anode, cathode, electrode].
(f) Reduction is the addition of [oxygen, hydrogen, nitrogen].
(h) Oxidation is the [gain, loss, acceptor] of electrons.
4. Match each of the items in List A with the appropriate items given (7 marks)
in List B.
List A List B
(a) alkali metal (i) produce emf
(b) pipette (ii) Cuo
(c) chemical cell (iii) indicate the end point
(d) Inert electrode (iv) Coke
(e) Oxidizing agent (v) to withdraw a known volume
(f) indicator (vi) lowest electron affinity
(g) Reducing agent (vii) Pt
5. Define the following. (8 marks)
(a) Electronegative elements
(b) Reduction in terms of Oxygen
(c) Relation between temperature and pressure of gases
(d) Conductor
(e) Covalent Bond
(f) Noble gas
(g) Stoichiometry
(h) Anode
SECTION (B)
6. Answer ALL question. (12 marks)
(a) What are the charges and masses of neutron and electron?
(b) Which law represents each of the following statements?
(i) The pressure of a gas will increase when it is heated.
(ii) A volume of gas expands when it is heated.
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(c) How many cubic centimeters of a 0.2M solution must be diluted with water to
make 4.0 dm3 of 0.025M?
(d) Write down the reactions at the cathode and anode for the electrolysis of
aqueous sodium chloride solution using Pt electrodes.
(e) State which reactant is oxidized and which reactants are reduced.
So2 + NaClO NaCl + H2SO4
(f) What is the oxidation number of the underlined element in the following?
(i) PCl3 (ii) N2O
7. Answer any FIVE questions. (20 marks)
(a) Write down the (i) essential electronic structure
(ii) group number
(iii) period number and
(iv) valence of 18Ar and 15P
(b) The element A,B and C are given with the following electronic structures.
A(2.8.1) B(2.8.7) C(2.3)
(i) Name the type of bonding exists between element B and C
(ii) Write down the electron dot-cross structure of the above compound.
(iii) Name the type of bonding exists between element A and B.
(iv) Which element has the lowest ionization energy?
(c) Helium gas diffuses twice as fast as a gas X. Calculate the molar mass and
relative density of the gas X. (He = 4)
(d) At 27 and 750 mmHg, a gas occupies 380 cm3. What is the volume of the gas
at STP?
(e) What volume of 2.0 M sulphuric acid is required to react with 5.0 g of zinc?
(Zn = 65.4, H = 1, O = 16)
(f) On passing a steady current of 0.75A for 25 minutes through a copper(II)
sulphate solution, 0.369 g of copper is deposited. Calculate the relative atomic
mass of copper.(One Faraday = 96500 coulombs)
(g) What will be the quantity of electricity required for the deposition of 1.8 g of
silver on the cathode? (One Faraday = 96500 coulombs, Ag = 108)
(h) What is an oxidizing agent? Give an example of a common oxidizing agent.
What is a reducing agent? Give an example of a common reducing agent.
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8. Answer any FOUR questions. (32 marks)
(a) (i) What type of electrodes are used in the electrolysis of molten lead (II) bromide?
Write equations for the reactions taking place at the electrodes.
(ii) Calculate the time required to discharge 0.835 g of copper by passing a current
of 0.3 A through and excess of copper (I)) sulphate solution.(Cu = 63.54)
(b) (i) Give the maximum number of electrons in number 2 shell and number 4 shell.
(ii) Classify the following elements as a alkali metal, alkaline earth metal, halogen
and noble gas.
11Na, 17Cl, 18Ne, 12Mg
(iii) What type of chemical bond is formed between NH3 and H+ ion? Explain.
(iv) Select and give reason which one has the larger radius from the following pair.
Na and Na+
(c) (i) Does the following reaction represent oxidation-reduction reaction(redox
reaction)? If redox reaction, State which reactant is oxidized and which reactant
is reduced and identify the oxidizing agent and reducing agent in the following
reaction.
3H2SO3 + 2HNO3 3H2SO4 + 2NO + H2O
(ii) Which one diffuses faster in each of the following pairs under comparable
conditions?
He and Ne ; CO2 and NH3
(d) (i) A certain mass of a gas occupies 300 cm3 measured at 31 . At what
temperature in will the gas occupy 285 cm3 at the same pressure?
(ii) 3g of a mixture of sodium carbonate and sodium chloride were made up to 250
cm3 of solution. 25 cm3 of this solution required 20 cm3 of 0.1050 M HCL for
neutralization. Calculate the percentage by mass of sodium carbonate in the
mixture. ( Na = 23, C = 12, O = 16)
(e) (i) The volume of a certain mass of gas occupies 968 cm3 at 515 mmHg. What is
the volume under 768 mmHg at the same temperature?
(ii) Vinegar contains the organic acid, acetic acid (ethanoic acid), HC2H3O2 . When
6 g of vinegar was titrated with 0.10 M sodium hydroxide, 40.00 cm3 of this
base had to be added to reach the equivalence point. What is the percentage by
mass of acetic acid in this sample of vinegar? ( H = 1, C = 12, O = 16)
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(f) Balance the following redox reactions using either oxidation number method or ion-
electron (half –reaction) method.
(i) K2Cr2O7 + H2SO4 + FeSO4 Cr2(SO4)3 + Fe2(SO4)3 + K2SO4 + H2O
(ii) Cl2 + NaOH NaCl + NaClO3 + H2O
(iii) H2SO4 + C CO2 + SO2 + H2O
(iv) Cu + HNO3 Cu(NO3)2 + H2O + NO
