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Sch 101 Introduction To Physical Chemistry Question Paper
Sch 101 Introduction To Physical Chemistry
Course:Bachelor Of Science
Institution: Pwani University question papers
Exam Year:2012
UNIVERSITY EXAMINATIONS
1stYEAR EXAMINATION FOR THE DEGREE OF
BACHELOR OF SCIENCE
COURSE CODE/TITLE:
SCH 101: INTRODUCTION TO PHYSICAL
CHEMISTRY
END OF SEMESTER:I
Useful constants
Gas constant R = 8.21 × 10-2
L. atm. K-1mol-1or 8.31 J K-1mol-1
, Density of air = 1.293 × 10-3g cm-3
at s.t.p,M3 = 106cm3
. S.t.p conditions; temperature = 273k
, Pressure= 760mmHg or 100,000pa.
Faraday constant = 96,485 C,L = 6.022 × 1023particles, Ksp for PbCl2 is 1.7*10-5 M 3.Fe2+/Fe, E0 = -0.409V, Zn2+ /Zn, E0 = -0.762 V
Instructions: Answer All Questions in Section A and any Two Questions in Section B
Section A: Answer All Questions
(40 marks)
Question One
a)Briefly explain the following terms:-
i)Gay-Lussac’s law
ii)Colligative property
iii)Common ion effect(3 marks)
b)i)At 25.0 °C and 9.0 atm.pressure, 1.50 L of a gas weighs 8.83 g. What is the molecula mass of the gas, if it is ideal? (3marks)
ii)A flask was weighed full of air and then full of methane.
The data obtained is shown
below:-
Volume of flask = 115 cm3
Mass of flask = 51.13 g
Mass of flask plus methane = 51.07 g
Temperature = 20 degrees Celsius
Pressure=10050 Pa
Calculate the molar mass of methane(6marks)
c)i)State two difference between a perfect gas and a real gas(2marks)
ii)Given that 4.50 moles of methane occupy 6.50 L at 50°C. Calculate the pressure of the gas in (atm) using the Van der Waals equation (a=2.25 atm.L2 mol-2b=0.0428 Lmol-1)And compare with the pressure of an ideal gas at the same temperature and molar
volume. (5 marks)
d)Consider the reaction;
H2 (g) +I2 (g)? 2HI (g); kc= 54.3
Given that the initial concentration of hydrogen, Iodine and hydrogen iodide are 0.0063M, 0.00414M and 0.0224M respectively. Calculate the concentration of the species at equilibrium.(5 marks)
e)i)A glass of water holding a volume of 250 mL is sweetened with 7.5 g sucrose C12H22O11.
Determine the freezing point depression resulting from this process.
(4marks)
ii)Calculate the molar solubility of silver bromide in pure water and in 0.01M Potassium
bromide
(ksp= 7.7 × 10-13M, Ag = 108, Br =80).(4 marks)
f)using a temperature composition diagram, explain briefly how a miscible mixture containing component
[A]which is more volatile than [B]can be separated(5 marks)
g)Outline three factors that affect the solubility of a salt.(3 marks)
Section B: Answer any Two Questions (30marks)
Question 2
a)Show that for the reaction:
2SO2(g) + O2(g)2SO3(g) Kp = Kc (RT)-1
where Kp and Kc are the equilibrium constants for pressure and concentration respectively. (8marks)
b)State three colligative properties of solutions(3 marks)
c)At 298K, 100 cm3 of a solution containing 3.002 g of an unidentified
solute exhibits an osmotic pressure of 2.55 atm. What is the molecular mass of the solute?(5marks)
Question Three
a)A mixture of gases contains 3.50 moles of ethane, 1.35 moles of neon and 3.21 moles of xenon. If the total pressure is 2.15, calculate the partial pressures of the gases.(6marks)
b)i)The solubility of magnesium hydroxide at 298 K is 1.71 x 10-4mol/L
. Calculate the solubility product.(4marks)
ii)What is the solubility of PbCl2in 0.10 M NaCl and in pure water(5marks)
Question Four
a)i)Differentiate between an electrochemical cell and electrolysis(2marks)
ii)Describe any two applications of electrochemistry in industry(4 marks)
b)Given the following reaction:-
Fe2+ + Zn (s)?Fe (s) + Zn 2+
i)Write down the half-cell and the overall reactions(3 marks)
ii)Calculate the EMFof the cell at 298kand deduce whether reaction is spontaneous or not.(3 marks)
iii)Calculate the equilibrium constant for the above reaction at 298k
(3marks)
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