CHEMISTRY HSSC-I
SECTION-A (Marks 17)
Time Allowed: 25 Minutes
(Revised Syllabus)

Note: Section-A is compulsory and comprises pages 1-2. All parts of this section are to be answered on the question paper itself. It should be comprised in the first 25 minutes and handed over to the Center Superintendent. Deleting/overwriting is not allowed . Do not use lead pencil.

1. Circle the correct options i.e. A / B/ C/ D. Each part carries one mark.

• Which sample contains the greatest number of molecules?

(A) 1.0 g of CH₄
(B) 1.0 g of H₂O
(C) 1.0 g of HNO₃
(D) 1.0 g of N₂O₄

• Which of the following sets of quantum numbers is NOT permissible?

(A) n=1, I=0, m=0, s=+1/2
(B) n=1, I=0, m=0, s=+1/2
(C) n=4, I=4, m=-3, s=+1/2
(D) n=2, I=1, m=0, s=+1/2

• On the basis of VSEPR theory, a molecule with three bond pair and no lone pair of electrons will have a structure:

(A) Linear
(B) Trigonal planar
(C) Tetrahedral
(D) Trigonal pyramidal

• If a sample of CH₄ effuses at a rate of 9.0 mol per hour at 35⁰C, which of the gases below will effuse at approximately twice the rate under the same conditions?

(A) CO
(B) He
(C) O₂
(D) F₂

• Consider the frictional reaction: CD (g) + D (g) ͇ C(g) + D_2(g)

(A) K_P = K_C
(B) K_C = K_P (RT)²
(C) K_C = K_P (RT)^-2
(D) K_C = K_P (RT)²

• The oxidation number of Cl in HCLO4 is:

(A) -1
(B) +1
(C) +5
(D) +7

• The following mechanism has been proposed for the reaction of NO and BR₂ to form NOBr:
  NO(g) + Br₂ (g)→ NOBr(g)
  NOBr₂(g) + NO(g) → 2NOBr(g)
  If the second step is rate determining step, the order of the reaction with respect to NO(g) is:

(A) 0
(B) 3
(C) 2
(D) 1

• The enthalpy of formation of CO₂ is -394kJmol^-1 . The enthalpy change for the reaction 2CO₂ (g) → 2C(s)+ 2O₂ (g) is:

(A) +92kJ
(B) +788kJ
(C) +92kJ
(D) +23kJ

• Which of the following aqueous solutions will have the highest boiling point?

(A) 0.20 m glucose
(B) 0.10 m NA₂SO₄
(C) 0.25 m sucrose
(D) 0.10 m NaCl

• The molecules of CO₂ in dry Ice from the:

(A) Ionic crystals
(B) Covalent crystals
(C) Molecular crystals
(D) Any type of crystal

• If a liquid has pH of 7 then:

(A) It must be colourless
(B) Its boiling point must be 100⁰C
(C) It must be a solution
(D) It must be neutral

• Which one of the following oxides is amphoteric oxide?

(A) CO₂
(B) SO₂
(C) CO
(D) ZnO

• Consider three one-liter flasks labeled A, B and C filled with the gases NO, NO₂ and N₂O, respectively , each at STP. Which flask contains the fewest molecules?

(A) Flask A
(B) Flask B
(C) All the same
(D) Flask C

• The wavelength of green light is 500 nm. Its frequency is equal to:

(A) 6x10¹⁴ Hz
(B) 6 Hz
(C) 1.5 Hz
(D) 1.5x10² Hz

• The normal boiling point of diethyl ether is 34.6⁰C and of water is 1000C. Which has the higher vapor pressure at 20⁰C?

(A) Water
(B) Diethyl ether
(C) They are the same
(D) It depends upon elevation

• The stoichiometric calculation of a chemical reaction results in :

(A) Actual yield
(B) Theoretical yield
(C) Percentage yield
(D) None of these

• If ∆H value is less than zero then reaction will be:
  

(A) Exothermic
(B) Endothermic
(C) May or may not be Exothermic or Endothermic
(D) None of these

CHEMISTRY HSSC-I
(Revised Syllabus)
Time Allowed: 2:35 Hours
Total Marks Sections B and C : 68

Note: Section’B’ and ‘C’ comprise pages 1-2 and questions therein are to answered on the separately provided answer book. Answer any fourteen parts from Section ‘B’ and attempt any two questions from section ‘C’. Use supplementary answer sheet i.e. Sheet-B if required.Write your answers neatly and legibly.

SECTION-B ( Marks 42)

Attempt any FOURTEEN parts. The answer to each part should not exceed 5 to 6 lines. (14 x 3 = 42)

• CuCl₂ + 2NaNO₃ → Cu(NO₃)₂ + 2NaCl
  If 15 grams of copper (II) chloride react with 20 grams of sodium nitrate, how much sodium chloride can be formed? (atomic mass Cu=64 g/mol, Cl= 35.5 g/mol, O=16 g/mol, Na=23g/mol, N=14 g/mol)
• Define the following:
• Pauli’s exclusion principle
• Hund’s rule
• Aufbau principle
• Methane water and ammonia are AB₄ type molecules but they have different molecular geometries given reason.
• If 90.0g C₆H₁₂O₆ is dissolved in 255g of H2O what will be the boiling point of the resulting solution?(Kb=0.52)
• Time required for given volume of N2 to diffuse through an office in 35 second if same volume of an unknown gas take 50 seconds to diffuse the same office under same conditions then calculate molar mass of unknown gas.
• What are amphoteric oxides? Give two examples.
• 4HCl (g) + O₂ (g) → 2H₂O(l)+2 Cl₂ ∆H = ?
  Calculate the enthalpy change of the above reaction from the following data:
  H₂(g)+1/2 O₂ (g) → H₂O(g) ∆H = -285.8kJ
  2H₂O(l) → 2H₂O(g) ∆H = -40.7kJ
  H₂(g)+ Cl₂ (g) → 2HCl (g) ∆H = -185kJ\
• What id Dolton’s Law of Partial Pressure? Give its two applications.
• What is the pH of a 1dm³ solution containing 0.240 mol CH₃COOH and 0.180 mol CH₃COONa?
  Ku(CH₃COOH) = 1.8 x 10 ^-5
• Hydrochloric acid is neutralized with Sodium hydroxide in the following reaction:
  HCL + NaOH → NaCl + H₂O ∆H = -57.68kJ/mol
  In a cofee cup calorimeter 100 cm³ of 1M HCl and 100 cm³ of 1M NaOH are mixed at 24.6⁰C.
  What is the final temperature of a mixture? Assume that density of both solution is 1.00g/ml and heat capacity of water is 4.18 j / gc⁰.
• Write three uses of electrochemical series.
• What are the factors affecting the surface tension of a liquid.
• Discuss the following properties of crystalline solids:
  
  • Isomorphism
  • Transition Temperature
• Write an expression for K_sp of PbSO₄?
• The value of K_sp is 1.96 x 10^-8. What is the solubility of PbSO₄?
• What is the effect of catalyst on the following?
  • The rate of reaction
  • The energy of activation
  • The equilibrium position of a reversible reaction
• Derive van der Waal’s equation for real gases.
• When 0.01 kg of CaCO₃ is decomposed. What is the volume of CO₂ produced at STP?
• In the equilibrium N₂(g) + O₂(g) ͇ NO(g) ∆H = 91.46kJ / m
  
• What is the effect on the position of equilibrium if?
  • Temperature is increased
  • Pressure is decreased
  • Any amount of nitrogen is added to the equilibrium mixture

SECTION-C (Marks 26)

Note: Attempt any TWO questions. All questions carry equal marks. ( 2x 13 = 26 )

Q.3 (a) How will you explain that elevation in boiling point is a colligative property? (03)
(b)Define osmotic pressure. Mention daily life applications of osmosis.(04)
(c) Calculate the concentration of solute in parts per million of the following mixtures: (06)
(i) If 500 mg of Ca⁺² is present in 2.5 g tablet
(ii) If 22 mg of Ca⁺² is present per kilogram of solution
(iii) If 0.006 g of Mg⁺² is present per kilogram of solution

Q.4 (a) Give the postulates of Kinetic Molecular Theory of Gases. (03)
(b) Gases do not show ideal behaviours at very low temperatures or very high pressures. Explain why? (04)
(c) One mole of CO₂ gas is maintained at 300 K. Its volume is 250 cm³. Calculate the pressure exerted by the gas under the conditions: (06)
(i) When gas is ideal
(ii) When gas is non-ideal (a = 3.590 atm dm⁶ mol ^-1 b = 0.0428 dm³mol ^-1  )

Q.5 (a) State lechatelier’s principle. How can one predict the effect of change in concentration and temperature upon chemical reaction at equilibrium using Lechatelier’s principle? (05)
(b)When a 0.218 mol sample of hydrogen iodide was heated in a flask of volume 1 dm³ , the following equilibrium was established at 700 K. (03)
2HI(g) H₂(g)+ I₂(g)
The equilibrium mixture was to contain 0.023 mol of hydrogen. Calculate the number of moles of iodine and the number of moles of hydrogen iodide in the equilibrium mixture.
(c) Define pH. Calculate the pH of .001 M H₂ SO_4. (03)
(d) Give two applications of Buffers. (02)