THE UNIVERSITY OF ZAMBIA
SCHOOL OF NATURAL SCIENCES
DEPARTMENT OF CHEMISTRY
ACADEMIC YEAR 2020
TERM 1
CHE1000: INTRODUCTION TO CHEMISTRY
5th April, 2022
TUTORIAL SHEET 2:
Students are advised to attempt all questions in order to prepare for the tutorials beginning
next week, and submit questions 1, 2, 4, 7, 15 and 18, as an assignment to be due on Friday,
8th at 16:00 hrs.
Note: Kindly submit your books to your tutorial group representatives who will later submit
to your respective tutors before the due date.
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1. In a redox titration, potassium permanganate, KMnO4, was standardized using a 19.60
g/L FeSO4(NH4)SO4.6H2O, (molar mass = 392.21 g/mol) standard solution. A 20.00 mL
of the FeSO4(NH4)SO4.6H2O standard solution, acidified with H2SO4 was put in a conical
flask. Potassium permanganate, KMnO4
was placed in the burette and the titration
conducted against 20.00 mL of the FeSO4(NH4)SO4.6H2O standard solution in the conical
flask.A titre volume 15.50 mL of KMnO4 solution was required to reach the end-point.
The titration reaction is:
3+
2+
Fe2+ (aq) + MnO−
4 (aq) → Fe (aq) + Mn (aq)
(i)
(ii)
(iii)
Balance the above redox reaction in basic medium.
Calculate the molarity of the 19.60 g/L FeSO4(NH4)SO4.6H2O, standard
solution.
Determine molarity of MnO4-(aq) in the burette.
2. A 0.2719 g sample containing 𝐶𝑎𝐶𝑂3 reacted with 20.00 mL of 0.2254 M HCl. Given that
HCl was excess. The excess HCl required exactly 20.00 mL of 0.1041 M NaOH to reach
the end-point using phenolphthalein indicator.
Determine percentage purity of 𝐶𝑎𝐶𝑂3 in the sample. The reaction involved is
𝐶𝑎𝐶𝑂3(𝑠) + 2𝐻𝐶𝐼(𝑎𝑞) → 𝐶𝑎𝐶𝐼2(𝑎𝑞) + 2𝐻2O(l)
The titration reaction is
𝐻𝐶(𝑎𝑞) + NaOH(aq) 𝑁𝑎Cl(𝑎𝑞) + 𝐻2𝑂(l)
3. If 2.45 mol of argon gas occupies a volume of 89.0 L, what volume will 2.10 mol of
argon occupy under the same conditions of temperature and pressure?
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4. A solid hydrocarbon is burned in air in a closed container, producing a mixture of gases
having a total pressure of 3.34 atm. Analysis of the mixture shows it to contain 0.340 g
of water vapor, 0.792 g of carbon dioxide, 0.288 g of oxygen, 3.790 g of nitrogen, and no
other gases. Calculate the mole fraction and partial pressure of carbon dioxide in this
mixture.
5. Define the following
(i) Titrant
(ii) Analyte
(iii) Standard solution
(iv)Concordant values
(v) Acid –base indicator
6. Suppose the sample 1.25 g sample of calcium carbonate is decomposed by heating to
calcium oxide and carbon dioxide. How many milliliters of carbon dioxide gas will be
evolved if the volume will be measured at 740 torr and 25oC?
7. Fluorocarbons are compounds of fluorine and carbon. A 45.60 g sample of a gaseous
fluorocarbon contains 7.94 g of carbon and 37.66 g of fluorine and occupies 7.40 L at
STP (P =1.00 atm and T = 273.15 K). Determine the approximate molar mass of the
fluorocarbon and give its molecular formula.
8. A liquid has an empirical formula CCl2, and a boiling point of 121oC. When vapourised,
the gaseous compound has a density of 4.93 g/L at 785torr and 150oC. What is the molar
mass of the compound and what is its molecular weight?
9. A sample of nitrogen collected in the laboratory occupies a volume of 725 mL at a
pressure of 0.971 atm. What volume will the gas occupy at a pressure of 1.40 atm,
assuming the temperature remains constant?
10. A sample of argon has a volume of 0.43 mL at 24°C. At what temperature in degrees
Celsius will it have a volume of 0.57 mL?
11. A cylinder of compressed gas has a pressure of 4.882 atm on one day. The next day, the
same cylinder of gas has a pressure of 4.690 atm, and its temperature is 8°C. What was
the temperature on the previous day in °C?
12. Chlorine gas is collected by water displacement at a temperature of 19°C. The total
volume is 1.45 L at a pressure of 156.5 kPa. Assume that no chlorine gas dissolves in the
water. What is the volume of chlorine corrected to STP?
13. If you placed 3 moles of N2 and 4 moles of O2 in a 35 L container at a temperature of
25°C, what will the pressure of the resulting mixture of gases be?
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14. I have a balloon that can hold 100 L of air. If I blow up the balloon with 3 moles of
oxygen gas as a pressure of 1 atmosphere, what is the temperature of the balloon?
15. Determine the pressure in atm exerted by 1 mole of methane placed into a bulb with a
volume of 244.6 mL at 25°C. Carry out two calculations: in the first calculation, assume
that methane behaves as an ideal gas; in the second calculation, assume that methane
behaves as a real gas and obeys the van der Waals equation. [Hint: the van der Waals
constant are available in your textbook.]
16. Engineers design automobile air bags that deploy most instantly on impact. To do this, an
air bag must provide a large amount of gas in a very short time. Many automobile
manufacturers use solid sodium azide, NaN3, along with suitable catalysts, to provide the
gas that is needed to inflate the air bag. The balanced equation for this reaction is:
2NaN3(g) → 2Na(s) + 3N2(g)
(i)
What volume of nitrogen gas will be produced if 117.0 g of sodium azide are
stored in the steering wheel at 20.2°C and 101.2 kPa?
(ii)
How many molecules of nitrogen are present in this volume?
(iii)
How many atoms are present in this volume?
17. Consider the separate 1.00 L sample of He(g) and UF6(g), both at 1.00 atm and containing
the same number of moles. What ratio of temperatures for the two samples would
produce the same root mean square velocity?
18. The rate of effusion of a particular gas was measured and found to be 24.0 mL /min under
the same conditions, the rate of effusion of pure methane (CH4) gas is 47.8 mL/min. what
is the molecular mass of the unknown gas?
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