PSPM SK016 2005-2012

Page | 1

Chapter 1: Matter

SESSION 2005/2006

1. (a) Mass spectrum of copper is shown as follows:

Based on the figure,

i. Write all the isotopes of copper. ii. Determine the percentage abundance of each isotope. iii. Calculate the relative atomic mass of copper.

[4 marks]

(b) A sample of concentrated hydrochloric acid contains 38% HCl by mass and has a

density of 1.1977 g mL1

. For this solution, calculate its

i. molarity

ii. molality [6 marks]

SESSION 2006/2007

2. (a) Define nucleon number and isotope.

Give the number of protons, neutrons and electrons in each of the following species.

i. 7935 Br

ii. 13056 Ba 2+

[4 marks]

(b) A 50 mL of a saturated NaOH solution containing 52% NaOH by weight with a

density of 1.48 g mL-1

is used to prepare a 0.1 M NaOH solution. Determine the

initial concentration of NaOH solution and the amount of water required to prepare

the 0.1 M NaOH solution. [6 marks]

SESSION 2007/2008

3. (a) Compound A consists of the element C, H and O. The complete combustion of 4.624g of the compound A yielded 6.557g of CO2 and 4.026g of H2O. Determine

the empirical formula of compound A. [6 marks]

(b) The reaction between acetic acid, CH3COOH and barium hydroxide, Ba(OH)2 produces a salt. Determine the maximum mass of the salt obtained if 17.13g of

barium hydroxide is used. [4 marks]

69.0

31.0

63 65

Rel

ativ

e in

tensi

ty

m/e

PSPM SK016 2005-2012

Page | 2

SESSION 2008/2009

4 . (a) FIGURE 1 shows the mass spectrum for copper, Cu, atom which has been

identified to have two isotopes.

FIGURE 1

i. Define isotope. ii. Using the information given in FIGURE 1, calculate the abundance of each

isotope for Cu. [4 marks]

(b) Urea, (NH2)2CO is used as fertilizer and in animal feed. It is prepared by reacting

ammonia and carbon dioxide as shown:

2NH3(g) + CO2(g) (NH2)2CO(s) + H2O(l)

In a process, 637.2 g of ammonia is allowed to react with 1142 g of carbon dioxide.

i. Determine the limiting reagent in the reaction. ii. Calculate the mass of urea formed. [6 marks]

SESSION 2009/2010

5. An amount of 27.82 g of hydrated sodium carbonate crystals, Na2CO3.xH2O was dissolved in water and made up to 1000 mL. 25.00 mL of this solution was

neutralized by 48.80 mL of 0.1 M hydrochloric acid.

(a) Write an equation for the reaction between sodium carbonate and hydrochloric acid. [1 mark]

(b) Find the molar concentration of sodium carbonate neutralized by the hydrochloric acid and find the value of x. [7 marks]

(c) If 0.05 M sulphuric acid were used instead of hydrochloric acid in the above analysis, what would be the volume of the sulphuric acid needed?

[2 marks]

Relative

abundance Cu6329

Cu6529

62.9298 64.9278

62 63 64 65 66

Mass/charge

PSPM SK016 2005-2012

Page | 3

SESSION 2010/2011

6 (a) (i) Define relative atomic mass of an element.

(ii) A sample of chlorine consists of two isotopes Cl3517 and Cl37

17. The

relative atomic mass of chlorine is 35.5. Determine the percentage

composition of each isotope in the sample. [4 marks]

(b) An impure solid sample of iron is reacted with an excess of hydrochloric acid,

HCl, to form an aqueos solution of iron (II) chloride, FeCl2 and H2 gas.

Assume that the impurities do not react with HCl.

(i) Write a balanced equation for the reaction.

(ii) When a 0.274 g of the impure iron is reacted with an excess of

hydrochloric acid, HCl, an amount of 8.54 x 10-3

g of H2 gas is

evolved. Calculate the percentage of iron sample. [6 marks]

SESSION 2011/2012

7 (a) Saline solution is prepared by dissolving 9.0 g of NaCl in deionised water in

A 500 mL volumetric flask. Calculate the molarity of the solution.

[3 marks]

(b) Nitric oxide, NO reacts with oxygen to produce nitrogen dioxide, NO2:

2NO (g) + O2 (g) 2NO2 (g) In an experiment, 0.53 mol of nitric oxide is mixed with 0.3 mol of oxygen.

Calculate the volume of NO2 produced at STP. [4 marks]

(c) Freon-12, CCl2F2 is used in various manufacturing industries. It is produced

from the reaction of carbon tetrachloride, CCl4 with antimony trifluoride,

SbF3:

3CCl4 + 2SbF3 3CCl2F2 + 2SbCl3

If 130g of CCl4 is mixed with 95.0 g SbF3, calculate

i) The amount (in grams) of CCl2F2 obtained.

ii) The amount of excess reactant after the reaction is completed.

[8 marks]

PSPM SK016 2005-2012

Page | 4

SESSION 2012/2013

8 (a) TABLE 1 show the atomic structure of four particles, represented by the letter A toD.

The particles are atoms and ions.

TABLE 1

Use the letter A to D to answer the following questions.

(i) Which two particles are atom and ion of the same element? Explain. [2 marks]

(ii) Which particles are isotopes of the same element? Explain. [2 marks]

(b) Compound E is a hydrocarbon, CxHy. When 6.84 g of this compound is burnt

completely in pure oxygen, 21.5 g of CO2 and 8.87 g of H2O are obtained. Determine

the empirical formula of compound E. If the molar mass of the compound is 128.2 g

mol-1

, what is its molecular formula? [6 marks]

(c) The reaction between the solutions of permanganate ion, MnO4-, and oxalate ion,

C2O42-

in acidic medium is shown below:

MnO4- + C2O4

2- MnO2 + CO2

Write

(i) the half-reactions for the redox reaction. (ii) the balanced redox equation for the reaction. [5 marks]

Particle Electrons Protons Neutrons

A 6 6 6

B 12 12 12

C 10 12 12

D 6 6 8

heat

PSPM SK016 2005-2012

Page | 5

Chapter 2 : Atomic Structure

SESSION 2005/2006

1. (a) Figure below shows the line spectrum of hydrogen atom in the visible region.

i. Draw the energy levels in a hydrogen atom. ii. Show the electron transitions which produce the above lines. iii. Give the name of this particular series of lines. [5 marks]

(b) State Aufbau principle and Hunds rule. Based on the principle and rule above, show how the electronic configuration of element 26G is built.

Draw the dxy

and dx

2y2 orbitals in 26G and the possible azimuthal and magnetic

quantum numbers for each of the orbital. [8 marks]

SESSION 2006/2007

2. (a) Write the electron configuration of iron(II) and iron(III). Determine the values of n, , m and s for the electrons in the outermost shell in iron(III).

Compare the size of these two ions. [8 marks]

SESSION 2007/2008

3. (a) Name the two transition elements that show anomaly in their electronic configurations. Write the electronic configuration and explain your answer. [6 marks]

(b) State the success and failure of Bohr`s atomic model.

Calculate the wavelength for a spectral line produced when an electron falls from n =

5 to n = 3. Name the series and state the region of electromagnetic spectrum for the

line. [8 marks]

SESSION 2008/2009

4. (a) i. A hydrogen atom requires a minimum energy of 2.18 x 10-18 J atom-1 to remove an electron from its ground state level. Determine whether a blue-violet light

with a wavelength of 434.0 nm can affect this process.

ii. The excited electrons of a group of irradiated hydrogen atoms are randomly

scattered to n = 1, 2, 3, and 4 energy levels. Draw an energy level diagram to

show all possible lines produced when all these electrons drop to lower levels.

Identify the line which has the shortest wavelength. [5 marks]

red blue indigo violet

Frequency

PSPM SK016 2005-2012

Page | 6

(b) The proton number of elements J and K are 13 and 16 respectively. Draw the

orbital diagram for the valence electrons of each element.

Suggest the most stable ions for J and K. Write their respective electronic

configuration. [8 marks]

SESSION 2009/2010

5. (a) Find the number of electrons in a zinc atom with i. Orbital quantum number,l, equals to 1 ii. Magnetic quantum number,m, equals to -1 iii. l=3 and m=+1 iv. s=-1/2

[5 marks]

(b) Write an electronic configuration for argon and two oppositely charged ions

having the same electronic configuration as argon.

State how a line spectrum differs from a continuous spectrum.Draw four lines

in the visible region of the line spectrum of hydrogen and indicate the low and

high energy ends. [5 marks]

SESSION 2010/2011

6. (a) A line with a wavelength of 486.4 nm was observed in the Balmer series of the

emission spectrum of hydrogen.

i. Calculate its frequency

ii. Determine the initial and final values of the energy levels associated

with this emission.

iii. State the region of the electromagnetic spectrum in which the line is

found. [5 marks]

(b) State and explain the appropriate rules used to determine the arrangement of

electrons in atomic orbitals.

The proton number of copper is 29, Write the valence electronic configuration

of the copper atom. Give a set of quantum numbers for the valence electron

that occupy the s orbital of copper. [8 marks]

PSPM SK016 2005-2012

Page | 7

SESSION 2011/2012

7 (a) FIGURE 1 shows the Lyman series of the hydrogen line spectrum.

10.97 10.66 10.52 10.27 9.74 8.22

Wave number, m-1

FIGURE 1

Describe the formation of the line emission spectrum of hydrogen atom in the Lyman series.

Calculate the ionization energy (kJ mol-1

) of the hydrogen atom using FIGURE 1. Name two

species that exhibit similar line spectrum as that hydrogen atom. [10 marks]

SESSION 2012/2013

8. (a) Describe the formation of emission spectrum for hydrogen atom. Show and label

the first three series of electron transitions between energy levels.

An electron in a hydrogen atom is transferred from n = 5 to n = 3. Calculate the

energy of the photon emitted and the wavelength of the spectral line produced.

[8 marks]

(b) An element Q has proton number of 8. Draw the orbital diagram of the element.

Explain the two rules applied in arranging the electrons in the orbitals.

[5 marks]

PSPM SK016 2005-2012

Page | 8

Chapter 3 : Periodic Table

SESSION 2005/2006

1. (a) The proton number of element A is 34.

i. Write the electronic configuration of element A.

ii. Identify the group, period and block of element A in the Periodic

Table.

iii. Predict the stable oxidation number of element A. Explain. [5 marks]

(b) Figure below shows the variation in ionic radii for elements in the third period.

Discuss the variation in ionic radii in the above figure. [7 marks]

SESSION 2006/2007

2. (a) The proton numbers for elements A and B are 16 and 24 respectively. State their

position in the periodic table and give the set of quantum numbers for the 8th

electron of A and 23rd

electron of B. [5 marks]

(b) Explain the changes in atomic radius from

i. Li to Rb

ii. Na to Ar [5 marks]

(c) Define first ionisation energy.

Arrange the elements Al, B, Mg and N in an ascending order of the first ionisation

energy. Explain the trend. [7 marks]

SESSION 2007/2008

3. (a) The first six successive ionisation energies, IE, (MJ mol-1

) of element B is as follows:

Based on the data given, determine the block and group for B. Explain your answer.

[4 marks]

IE 1 IE 2 IE 3 IE 4 IE 5 IE 6

1.40 2.86 4.58 7.48 9.44 56.27

10 11 12 13 14 15 16 17 18 Number of

proton

Ionic

radiu

s/ar

bit

rary

unit

Na+ Mg

2+

Al3

+

Si4

+

P3

S2

Cl

PSPM SK016 2005-2012

Page | 9

(b) Describe the acid-base character of oxides of elements in period 3. For each type of

oxide, give one example and write a balanced chemical reaction that shows their acid-

base character. [7 marks]

SESSION 2008/2009

4. (a) FIGURE 2 shows part of a periodic table. The positions of nine elements are

indicated by letters not representing their usual symbols. Answer the following

questions based on this figure.

A B

C D E F

G H I

FIGURE 2

Identify the element which

i. has the largest ionic radius. ii. has the smallest atomic radius. iii. has the lowest first ionisation energy. iv. has the highest electronegativity. v. forms amphoteric salt with oxygen. [5 marks]

(b) The ionic radii of elements in the second period of the periodic table are given in

TABLE 1.

TABLE 1

Ion Li+

Be2+

B3+

N3-

O2-

F-

Radius (nm) 0.060 0.031 0.020 0.171 0.140 0.136

Explain the trend observed in the ionic radii. [7 marks]

SESSION 2009/2010

5. (a) Sodium,magnesium and silicon are elements in period . By referring to the type of

bonding and structure, explain the following:

i. Silicon has the highest melting point in the period.

ii. The melting point of magnesium is greater than that of sodium [5 marks]

PSPM SK016 2005-2012

Page | 10

(b) Referring to TABLE 1,explain why fluorides of Li,Be,Na, Mg and Al are solids whereas

fluorides of the other elements are gases.

TABLE 1

Period 2 LiF BeF2 BF3 CF4 NF3 OF3 F2

Solid Solid Gas Gas Gas Gas Gas

Period 3 NaF MgF2 AlF3 SiF4 PF3 SF6 ClF3

Solid Solid Solid Gas Gas Gas Gas

[7 marks]

SESSION 2010/2011

6. (a) Elements , and are found in the periodic table.

i. Determine the group and the period of = A.

ii. Write the electronic configuration for the ions B2+ and C2- .

iii. Which element has the largest atomic radius? Explain your answer. [5 marks]

(b) FIGURE 1 shows the variation in the first ionisation energy of the elements in the third

period. Explain the trend across the period.

FIGURE 1

[7 marks]

PSPM SK016 2005-2012

Page | 11

SESSION 2011/2012

7. For each the following elements:

Sodium, Magnesium, Aluminium and Silicon

Give the formula, type of bonding present and the acid-base character of its oxides. For those

oxide(s) that exhibit amphoteric behavior, write an appropriate chemical equation to illustrate

the properties.

[10 marks]

SESSION 2012/2013

8. Given four elements W, X, Y and Z with their proton numbers of 11, 12, 13 and 18,

respectively. Identify the group and period of the elements in the Periodic Table. Arrange the

elements according to increasing atomic radii and explain the trend.

[7 marks]