RAWALPINDI BOARD 2013
CHEMISTRY
PART-I
Time: 20 MM.
(Objective Part)
Marks: 17
Note: You have four choice for each objective type question as A, B, C and D. The choice which you think is correct; fill that circle in front of that question number. Use marker or pen to fill the circles. Cutting or filling two or more circles will result in zero mark in that question.

• For the reaction , H+ +H the change in enthalpy is called heat of:

(a) Reaction
(b) Combustion
(c) Solution
(d) Neutralization

• The pH of human blood is :

(a) 7.32
(b) 7.33
(c) 7.34
(d) 7.35

• pH = pKa + log  is known as :

(a) Einstein equation
(b) Plank equation
(c) Gibb's equation
(d) Handerson equation

• A thermometer used in Lands Berger's method can read up to:

(a) 0.1K
(b) 0.01 F
(c) 0.01
(d) 0.01°C

• Oxidation Number of chromium in Cr₂ O₇^-2 is:

(a) +3
(b) +4
(c) +5
(d) +6

• Standard Hydrogen Electrode (SHE) is made of :

(a) Ag foil
(b) Au foil
(c) Cu foil
(d) Pt foil

• Arrhenius equation is represented as :

(a) A=K^-EaIRT
(b) A= K^eRTI-Ea
(c) K = Ae^RTI-Ea
(d) K = Ae^-EaIRT

• Tin has Isotopes:

(a) 8
(b) 9
(c) 10
(d) 11

• The number of moles of CO₂ which contain 8.0g of oxygen is:

(a) 0.25
(b) 0.5
(c) 1.0
(d) 1.50

• The drying agent used in a desiccator is:

(a) NaCl
(b) KBr
(c) CaCl₂
(d) BaCl₂

• The S.I unit of pressure is expressed in :

(a) Nm^-1
(b) Nm^-2
(c) Nm^-3
(d) mmHg

• Cholesteryl benzoate turns into milky liquid at:

(a) 144°C
(b) 145°C
(c) 146°C
(d) 147°C

• When a =b ≠ c and a = β = 90°, y = 120° then system is:

(a) Cubic
(b) Triclinic
(c) Hexagonal
(d) Monoclinic

• Cathode rays cause a chemical change because they have-----------effect:

(a) Oxidizing
(b) Conducting
(c) Reducing
(d) Diffusing

• Quantum Number values for 2p orbitals are:

(a) n = 2 , 1 = 1
(b) n = 1 , 1 = 2
(c) n = 1,1=0
(d) n = 2, 1= 0

• The radius of Na⁺¹ ion is:

(a) 92 pm
(b) 93 pm
(c) 94 pm
(d) 95 pm

• Bond order of O₂^-2 is:

(a) Zero
(b) One
(c) Two
(d) Three

Section-II

2. Attempt any EIGHT short questions.

• Why atoms cannot be abserved by an ordinary optical microscope?
  
• How the colouring impurities are removed from a crude substance?
  
• Why do we get straight line when pressures are plotted against the inverse of the volumes for a gas?
  
• Heat of sublimation of a substance is greater than that of heat of vapourization. Justify it.
  
• What are monoisotopic elements? Give two examples.
  
• Write down two stoichiometric assumptions.
  
• Mention important uses of chromatography.
  
• Write down two causes for the deviation of gases from ideality.
  
• Give the units of Vander Wall constants "a" and "b".
  
• Why HF is a weaker acid than HCI? 
  
• Differentiate between polymorphism arid allotropy.
  
• Why metals behave as good conductors of electricity?

3. Attempt any EIGHT, short questions.

• How the emission of a β particle results in the increase of atomic number of an element?
  
• How the charge to mass ratio of an electron helps to determine the mass of an electron?
  
• What is the origin of the emission of line spectrum of an atom?
  
• Give the basic assumptions of "Valence Shell Electron Pair Repulsion" (VSEPR) theory.
  
• What information’s about the molecular structure are obtained from the dipole moment?
  
• Why is it necessary to mention the physical states of reactants and products in a thermo chemical reaction?
  
• What is the justification for the increase of ionic product of water with temperature?
  
• π-bonds are more diffused than σ bonds. Give reasons.
  
• Define Pauli's exclusion principle and Hund's rule.
  
• Define orbital hybridization and overlapping of orbitals.
  
• Define enthalpy of combustion and enthalpy of solution.
  
• Define acid and base by Lowery-Bronsted concept.

4. Attempt any SIX short questions.

• Why aqueous solution of NH₄C1 is acidic but that of CH₃COONa is basic?
  
• Zn can displace hydrogen from acids but Cu cannot do so. Why?
  
• Calculate the oxidation number of phosophorous in :
  
  • (a) HPO₃
    
  • (b) Na₃PO₄
    
• Differentiate between homogeneous and heterogeneous catalysis.
  
• Differentiate between average and instantaneous rate of reaction.
  
• How does K_o value tell about extent of a reaction?
  
• Define molarity . Give its mathematical expression.
  
• What is Raoult law?
  
• Define standard electrode potential.

Attempt any THREE questions.

5. (a) What are covalent solids? Discuss the structure of diamond.
(b) When lime stone (CaCO3) is roasted quickline (CaO) is produced according to the following equation. The actual yield of (CaO) is 2.5 kg. When 4.5 kg of lime stone is roasted . What is percentage yield of this reaction?
CaCO₃(s)→ CaO(s)+CO₂(g)
[ At. wt. of Ca is 40, C is 12 and that of O is 16 a.m.u.]

6. (a) Explain the paramagentic behaviour of oxygen using molecular orbital theory.
(b) Define and explain Hess's law of constant heat summation.

7. (a) Explain Graham's law of diffusion . Give its experimental verification.
(b) Give the postulates of Bohr's atomic moder:

8. (a) Describe the electrolysis of t'used.salts and aqueous solutions of salt.
(b) The solubility PbF₂ at 25°C is 0.64 g dm-3. Calculate Ksp of PbF₂ Mol mass of PbF₂ is 245.2.

9. (a) How molecular mass of an orginic compound is determined by Landsberger's method?
(b) How order of a reaction is determined by Half Life method?

Attempt any THREE questions.

10. (a) The given solution contains 6g of a mixture of HC1 and NaCl dissolved per dm³. Determine the percentage of NaCl in the mixture.
(b) Determine the number of molecules of water of crystallization in a given sample of oxalic acid by permanganate titration. The amount of oxalic acid dissolved per dm³ is 6.3g (Molecular mass of (COOH)₂ = 90)
(c) Determine the amount dissolved per dm3 of lodinic in the given sample.
(d) Purify commercial NaCI by passing HC1 gas.
(e) Separate a mixture of various inks by paper chromatography.