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1) Calcium oxide is commonly known as quicklime. Since it reacts readily with water,

it does not occur naturally and has to be produced by heating limestone.

a) By using relevant data from the Data Booklet and the following data, construct

a labeled energy level diagram, showing clearly all the enthalpy changes

involved and the chemical species at each stage. Hence, use it to calculate

the lattice energy of calcium oxide.

kJ mol-1

Enthalpy change of atomization ofcalcium

+ 178

Enthalpy change of formation ofcalcium oxide

- 635

First electron affinity of oxygen - 147

Second electron affinity of oxygen + 753

b) Suggest and explain how the magnitude of the lattice energy of Ca3N2 might

compare with that of CaO. [7]

2) A container holds a gaseous mixture of nitrogen and propane. The pressure in

the container at 200 C is 4.5 atm. At -40 C, the propane completely condenses

and the pressure drops to 1.5 atm. Calculate the mole fraction of propane in the

original gaseous mixture. [3]

3) In an experiment to determine the standard enthalpy change of combustion of

butan-1-ol, Hc, a quantity of the fuel was burned underneath a 200 g copper can

containing 515 g of water. It was found that the temperature of water rose from23 C to 58 C after 2.30 g of butan-1-ol has been burned completely

a) Write an equation for the complete combustion of butan-1-ol.

b) Using experimental results and relevant data from the Data Booklet, calculate

the apparent Hc of butan-1-ol (ignoring the heat capacity of the copper can).

c) The true value of Hc of butan-1-ol is -2670kJ mol-1. Compare this value to

the one you have calculated in (iv) and suggest a reason for the discrepancy.

[5]

4) The identification of the elements in this question is restricted to proton number 1

to 20.

Elements A and B belong to the same group and element C belongs to the same

period as B.

Elements A and B have high melting points while element C has a low melting

point. The various oxides of A and C exist as simple discrete molecules while the

oxide of B exists as a giant molecular structure. Both elements A and B can

combine to form a compound with a high melting point.

Both elements A and B are insoluble in water while C readily reacts with water

resulting in an acidic solution and the resultant solution gives a white precipitate

with aqueous silver nitrate. When elements A and C react to form a compound D,

it is inert and does not dissolve in water. When elements B and C react to form acompound E, it is reactive towards water leading to the formation of an acidic

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solution and fine white solid.

Identify A to E, and explain your reasoning clearly. [9]

5) Nitrogen monoxide in the air can be converted to nitric acid, which results in acid

rain. Both nitrogen monoxide and nitrogen dioxide participate in ozone layer

depletion. One way of forming nitrogen monoxide is through the dissociation ofnitrogen dioxide.

2NO2 (g) 2NO (g) + O2 (g)

At 494 C, the value of Kp for the above reaction is 36.9 kPa.

When a certain partial pressure of nitrogen dioxide is put into an empty vessel at

494 C, equilibrium is reached when 45 % of the original nitrogen dioxide has

decomposed.

a) Write an expression for the equilibrium constant, Kp, for the reaction. [1]

b) Calculate the original partial pressure of nitrogen dioxide before any

dissociation occurred. [3]

6) Nitrous acid, HNO2, is an unstable, weakly acidic compound. It can easily be

prepared by acidifying a solution of a nitrite.

Barium nitrite, Ba(NO2)2 is often used since the insoluble barium sulfate can be

easily filtered off.

Ba(NO2)2 (aq) + H2SO4 (aq) 2HNO2 (aq) + BaSO4 (s)

Nitrite ions can be oxidized by potassium manganate (VII) to form nitrate ions.

The following are some thermochemistry data.

H / kJ mol-1

Enthalpy change of atomization of

barium

+175

Enthalpy change of Ba(s) Ba2+ (aq)+ 2e

+286

Enthalpy change of hydration of NO3- -325

Lattice energy of barium nitrate -1395

a) Write the equation between nitrite ions and potassium manganate (VII).

b) Using the data above, and relevant data from the Data Booklet, construct an

energy cycle to calculate the enthalpy change of hydration of the barium ion.

c) The Shydration of barium ion is -188 J mol-1 K-1. Explain why the sign of

Shydration is negative.

d) Hence, calculate G

hydration of barium ion at 298K.

e) Predict the effect of high temperature on the spontaneity of the above reaction.

f) Using your answer in (a), and relevant data from the table, calculate the

enthalpy change of solution of barium nitrate. [7]

7)