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Sch 2102: Physical Chemistry I Question Paper

Sch 2102: Physical Chemistry I

Course:Bachelor Of Pharmacy

Institution: Jomo Kenyatta University Of Agriculture And Technology question papers

Exam Year:2012

JOMO KENYATTA UNIVERSITY
OF
AGRICULTURE AND TECHNOLOGY

University Examinations 2012/2013
FIRST YEAR FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE OF PHARMACY

SCH 2102: PHYSICAL CHEMISTRY I

DATE: AUGUST, 2012 TIME: 2 HOURS

INSTRUCTIONS: Answer ANY FIVE Questions. Each Question Carries Twenty Marks.

h = 6.626 x 10-34 JS ; C = 3.0 x 108 m/s , RH = 2.18 x 10-18J

Question One

a) How do nuclear reactions differ from ordinary chemical reactions? [2 marks]

b) Complete the following nuclear equations and identify X in each case:

i. . [2 marks]

ii. [2 marks]

c) A radioactive Potassium – 40 isotope decays to argon – 40 with a half-life of 1.2 x 109 yr.

i. Write a balance equation for the reaction. [2 marks]

ii. A sample of rock is found to contain 18% potassium 40 and 82% argon by mass. Calculate the age of the rock in years. [4 marks]

e) Explain the following:

i. Nuclear decay. [2 marks]
ii. Nuclear transmutation. [2 marks]

f) State and explain two uses of radioactive isotopes. [4 marks]

Question Two

a) List the characteristics of a real gas.

b) State Boyle’s Law

c) At STP, 0.280L of gas weighs 0.400g. Calculate the molar mass of the gas.

d) A sample of air occupies 3.8L when the pressure is 1.2atm. Calculate its volume at 6.6atm maintaining its temperature constant.

e) A 2.5L flask at 150C contains a mixture of N2, He and Ne at Partial pressure of 0.32atm for N2, 0.15atm for He and 0.42atm for Ne.

i. Calculate the total pressure of the mixture.
ii. Calculate the volume in Litres at STP occupied by He and Ne if the N2 is removed
selectively.

f) Write the Van der Waals equation for a real gas explaining all the corrective terms.

Question Three

a) Define with examples:

i. Physical equilibrium [2 marks]

ii. Chemical equilibrium [2 marks]

b) i. State Le – chatelier’s principle. [2 marks]

ii. State and explain three factors upon which equilibrium depends. [6 marks]

c) A 2.50 mole quantity of NOCl was initially in a 1.50L reaction chamber at 4000C. After equilibrium was established, it was found that 28 percent of the NOCl had dissociated:

2NOCl(g) ? 2NO(g) + Cl2(g)

Calculate the equilibrium constant Kc for the reaction. [5 marks]

d) i. How does a reaction quotient differ from an equilibrium constant? [2 marks]

ii. If Q>K(eq) how must the reaction proceed to reach equilibrium? [2 marks]
Question Four

a) Define giving an example the following:

i. Bronsted acid. [2 marks]

ii. Bronsted base. [2 marks]

iii. A Lewis acid. [2 marks}

b) Calculate the concentration of H+ ions in a 0.62M NaOH solution. [3 marks]

c) A 0.0560g quantity of acetic acid is dissolved in enough water to make 50.0ml of solution.

i. Calculate the concentrations of H+ and CH3COO- and CH3COOH at equilibrium.
[6 marks]

ii. The pH of the acid. [2 marks]

d) A solution is made by dissolving 18.4g of HCl in 662ml of water. Calculate the pH of the solution. [3 marks]

Question Five

a) Explain the following:

i. Buffered solutions [2 marks]
ii. Buffer capacity [2 marks]
iii. Solubility [2 marks]

b) A buffer solution contains 0.12mol of propionic acid (HC2 H5O) and 0.10 mol. of sodium propionate. (NaC3H5O2) in 1.50L.

i. Calculate the pH of this buffer.
ii. Calculate the pH of this buffer after addition of 0.01mol. of NaOH.

(Ka HC3H5O2 = 1.3 x 10-5)

c) If the molar solubility of CaF2 at 350C is 1.24 x 10-3 mol/L, calculate the Ksp at this temperature. [2 marks]

d) Calculate the molar solubility of AgBr in 0.01M NaBr solution. (Ksp AgBr = 5.0 x 10-13)
[2 marks]

Question Six

a) i. What is meant by a Lewis structure of an atom? [1 mark]

ii. Draw Lewis structures for the following molecules/ions and predict their molecular geometry. [9 marks]

a) CS2 b) H3O+ c) SCN-

C = 6, S = 16, O = 8, N = 7

b) i. Define what intermolecular forces are. [1 mark]

ii. What intermolecular forces do you expect to find in the following species.
[9 marks]

I. CH3 CH2 CH2 OH

II. HCl

III. O2

c) i. Explain what is meant by Dilution. [2 marks]

ii. How many milliliters of 3.0M H2SO4 are needed to make 450ml of 0.10M H2SO4? [4 marks]

Question Seven

a) What is an atomic orbital? [2 marks]

b) i. Using s, p, d notation, write the electronic configuration of an atom X = 32.
[1 mark]

ii. What period and group does X belong to? [2 marks]

c) What is meant buy 3S1? [2 marks]

d) Calculate the wavelength of Radiation released when an electron moves from
n = 6 to n = 2. [5 marks]

e) Calculate the frequency of radiation whose wavelength is 600nm. [3 marks]

f) i. Define what is an electromagnetic radiation. [2 marks]

ii. Why do you think atoms always give a line emission spectrum? [2 marks]

Sch 2102: Physical Chemistry I Question Paper

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