Integrated Assignment
(C2H5OH) is currently blended with gasoline in some countries as an 1 Ethanol
automobile fuel.
(a) Write a balanced equation for the combustion of liquid ethanol in air.
(b) Calculate the standard enthalpy change for the reaction, assuming steam as a
product.
(c) Calculate the heat produced per dm3 of ethanol by combustion of ethanol under
constant pressure.
CO2 gas produced in the automobile fuel traps the heat much like the glass of (d) The
a greenhouse and has an effect of increasing the surface temperature of the Earth.
(i) Use your answer to (b) to calculate the mass of CO2  produced per kJ of heat
emitted.
(ii) Name another greenhouse gas.
(e) Ethanol is fully soluble in water. Draw a diagram to illustrate the interaction
between ethanol and water molecules, show any relevant lone pairs and dipoles.  Data required for this question:
•Standard enthalpy change of formation of C2H5OH(l) = –277.7 kJ mol–1•Standard enthalpy change of formation of CO2(g) = –393.5 kJ mol–1
•Standard enthalpy change of formation of H2O(g) = –241.8 kJ mol–1
•Density of ethanol = 0.789 g cm–3
2 An exhaled breath of air consists of 74.8 % N2, 15.
3 % O2, 3.7 % CO2 and 6.2 %
water vapour.
(a)  If the total pressure of the gases is 0.980 atm., calculate the partial pressure of
CO2 in the mixture.
(b) If the volume of the exhaled gas is 455 cm3 and its temperature is 37 o C, calculate
the number of mole of CO2 exhaled.
(c) The oxidation for the metabolism of glucose (C6H12O6) in our body is the same as
that for combustion of C6H12O6 except that the reaction in the body takes place in
a series of steps that occur at body temperature.
i)    Write a balanced equation for the metabolism of glucose in the body.
ii)  Hence, calculate the mass of glucose needed to be metabolized to produce the quantity of CO2 in (b).
3(a)    A method used by the US Environmental Protection Agency for determining the concentration of ozone in the air is to pass the air sample through a ‘bubbler’ containing sodium iodide, which removes
the ozone according to the following equation:
O3(g)  +  2NaI(aq)  + H2O(l) → O2(g)  +  I2(s)  +  2NaOH(aq)
(i)  In the reaction, the iodide ion is oxidized to iodine. Identify the oxidizing agent
and justify how it can be considered so.
(ii)  Calculate the mass of sodium iodide are needed to remove 1.3 mg of ozone in an air sample.
(b) Iodine is an insoluble black solid; but it can be made to dissolve in potassium
iodide owing to the formation of the complex tri-iodide ion:
I2(s)  +  I–(aq)        I3–-(aq)
Explain as clearly as you can why iodine cannot dissolve in water, but the complex
reaction mass
tri-iodide ion can.
(c)  State and explain the difference in the electrical conductivities of NaI in the aqueous
state and solid state.
4 The iodate(V) ion is reduced by sulphate(IV) ion according to the following
equation:
IO3–(aq)  +  3SO32– (aq) → I– (aq)  +  3SO42– (aq)
The rate of this reaction is 1st order with respect to IO3–, SO32– and H+.
(a) Write the rate equation for this reaction.
(b) By what factor will the rate of the reaction change if the pH is lowered from 5.0 to
3.5?
(c) Explain clearly how the reaction can be pH-dependent even though H+ does not
appear in the overall reaction.
5 The following mechanism has been proposed for the gas-phase reaction of H2 and
ICl:
H2 (g) +  ICl(g) →  HI(g)  +  HCl(g)                  slow
HI(g)  +  ICl(g) →  I2(g) +  HCl(g)                    fast
(a) For this reaction, give
(i)  the stoichiometric equation
(ii) the rate equation
(b) (i)  Define bond energy.
(ii) Using relevant data from the Data Booklet and the bond energy of I-Cl is      208 kJ mol–1, calculate the enthalpy change for the gas-phase reaction.
(c) Draw an energy profile diagram for the reaction, labeling fully the chemical species
present at each stage as the reaction progresses.
6 Sulfur tetrafluoride (SF4) reacts slowly with oxygen to form sulfur tetrafluoride
monoxide (OSF4), according to the following unbalanced equation:
SF4(g)  +  O2(g)  → OSF4(g)
(a) Balance the equation for the reaction.
(b) Draw the dot-cross diagram for the sulfur-containing species, and use VSEPR to
predict their shapes.
(c) The enthalpy change for the reaction is –551 kJ mol–1. Estimate the bond energy
between sulfur and oxygen, given that average bond energy between sulfur and
fluorine is 327 kJ mol–1.

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