CHAPTER 1.0 MATTER

TUTORIAL 1.0

MATTER

At the end of this chapter, students should be able to:

1.1 Atoms and a) Write isotopic notation

molecules b) Interpret mass spectrum

c) Calculate the average atomic mass of an element given the relative
abundances of isotopes or a mass spectrum.

1.2 Mole concept a) Define the terms empirical and molecular formulae.
b) Determine empirical and molecular formulae from mass composition or

combustion data.
c) Determine the empirical formula (formula unit) from experiment.

(Experiment 1: Determination of formula unit of a compound)

d) Define each of the following concentration measurements:
i. molarity (M);
ii. molality (m);
iii. mole fraction (X);
iv. percentage by mass (% w/w); and
v. percentage by volume (%v/v)

e) Calculate each of the following concentration measurements:
i. molarity (M);
ii. molality (m);
iii. mole fraction (X);
iv. percentage by mass (% w/w) and
v. percentage by volume (%v/v)

1.3 Stoichiometry a) Write a balanced chemical equation:
i. by inspection method; and
ii. by ion-electron method (redox equation)

b) Define
i. limiting reactant; and
ii. percentage yield

c) Perform stoichiometric calculations using mole concept including limiting
reactant and percentage yield.
(Experiment 2: Acid – Base Titration – Determination of the Concentration
of Hydrochloric Acid)
(Experiment 3: Determination of Molar Mass of a Metal)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 1

HOUR : 1

1. Mercury atom has 80 protons and 121 neutrons. Write the isotopic notation for mercury.
UPS 2012 / 2013 (CLO1, C1)

2. Complete the following table. (CLO1, C1)
Isotopic
Element No of subatomic particles Nucleon notation
number
pen 3157Cl
28
Silicon 14
24
Chlorine

Bromine 35 36 44

Magnesium 12 10

3. An ion Y3+ has 18 electrons and 24 neutrons.

a) Determine the proton number and nucleon number of the element Y.
b) Write the isotopic notation to represent the element. UPS 2015 / 2016 (CLO1, C1)

4. The mass spectrum of copper is shown in FIGURE 1. (CLO3, C4)

Relative intensity 69.0
31.0

63.0 65.0 Mass/charge

FIGURE 1

Based on FIGURE 1,
a) Write all the isotopes of copper.

b) Determine the percentage abundance of each isotope.

c) Calculate the relative atomic mass of copper. (63.62)

5. FIGURE 2 shows the mass spectrum of element X :
2.8

Relative abundance 1.5
0.89

m/e

50 52 56
FIGURE 2

a) State the number of protons and neutrons in isotope X52

27

b) Calculate the relative atomic mass of X. (52.11) UPS 2011 / 2012 (CLO3, C4)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 2

6. Element J has 10 protons. FIGURE 4 shows the mass spectrum of J.
90.48

% abundance

9.25
0.27

20 21 22 m/e
FIGURE 4

a) Write the isotopic notation of J with the highest percentage abundance.

b) Calculate the average atomic mass of J, if the isotopic masses are 19.9924 amu, 20.9938

amu and 21.9914 amu. (20.18 amu)

UPS DK015 2014 / 2015 (CLO3, C4)

HOUR : 2

7. Given the following table:

Isotope Mass (amu) Percentage
abundance
107Ag 106.91
109Ag 108.90 51.50
48.50

Calculate the average atomic mass of silver. (107.88 amu)
UPS 2014 /2015 (CLO3, C4)

8. Iron consists of 5.82% 54Fe, 91.66% 56Fe, 2.19% 57Fe and 0.33% 58Fe. The isotopic masses of these

four isotopes are 53.9396 u, 55.9394 u, 56.9354 u and 57.9333 u respectively. Calculate the relative

atomic mass of iron. (CLO3, C4)
(55.85)

9. The two naturally occurring isotopes of gallium are gallium-69 and gallium-71 which are found in the

ratio of 3:2. Determine the atomic mass of gallium. UPS 2008 /2009 (CLO3, C4)
(69.8 amu)

10. The isotopes of Ag occur naturally as 107Ag and 109Ag with their isotopic masses of 106.91 a.m.u and

108.87 a.m.u respectively. If the average atomic mass of Ag is 107.9 a.m.u, what would be the
percentage abundance of these two isotopes? (CLO3, C4)

(abundance of 107Ag =49.49%; abundance of 109Ag 50.51%)

11. Magnesium is an element with a proton number of 12. In a sample of magnesium, it was found that
magnesium atoms have three different nucleon numbers of 24, 25 and 26.
a) Write the symbol for one of these three atoms, showing its proton number and nucleon
number.

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 3

b) A sample of magnesium contains 78.6% of atoms with a nucleon number of 24, 10.1% of
atoms with a nucleon number of 25 and 11.3% of atoms with a nucleon number of 26.

Calculate the relative atomic mass of magnesium. (24.33)

c) Sketch and label the expected mass spectrum of the magnesium.

PSPM 2013 / 2014 (CLO3, C4)

HOUR : 3

12. Analysis of a gaseous hydrocarbon compound gives the following percent composition by mass:

85.7% C and 14.3% H.

a) Define empirical formula and molecular formula.

b) Determine the empirical formula of the hydrocarbon.
c) 0.25 g of this compound occupies a volume of 100 mL at STP. Determine the molar mass

and the molecular formula of the hydrocarbon (CLO3, C3)

(56.00 g mol−1)

13. Oxalic acid is often used to remove blood and rust stains. It contains 2.24% hydrogen, 26.65% carbon

and 71.08% oxygen by mass. The molar mass of oxalic acid is 90.0 g mol–1.

a) Determine the empirical formula of oxalic acid.

b) What is its molecular formula? PSPM JAN 1999 (CLO3, C3)

14. A complete combustion of a hydrocarbon forms 1.10 g of CO2 and 0.45 g of H2O. The molar mass is
84.00 g mol–1. Determine the empirical formula and molecular formula of the hydrocarbon.
(CLO3, C3)

15. A compound P, with the relative molecular mass of 46, contains the elements carbon, hydrogen and

oxygen. When 2.30 g sample of P is completely burnt in excess oxygen, 4.40 g carbon dioxide and

2.70 g water were produced.
a) Calculate the mass of carbon, hydrogen and oxygen in 2.30 g of P.

b) Determine the empirical formula and molecular formula of P.

c) Write a balanced equation for the combustion. PSPM JAN 2000 (CLO3, C3)

HOUR : 4 (1.2 g C, 0.3 g H, 0.8 g O)

16. Define the terms: (CLO1, C1)
a) molarity
b) molality
c) percentage by mass.

17. An aqueous solution contains 167 g CuSO4 in 820 mL of solution. The density of the solution is
1.195 g mL-1. Calculate the following:

a) molarity of the solution (1.28M)

b) percentage by mass of CuSO4 (17.00 %)

c) mole fraction of each component (0.0226, 0.9774)
d) molality of the solution (1.29 molal)

(CLO3, C4)

18. A certain amount of NaOH is dissolved in 98.0 g of water at 25 °C. The final volume of NaOH solution
is 100 mL. Given the density of the solution is 1.33 g mL-1 at 25 °C, calculate the number of moles

of NaOH used. (0.875 mol) UPS 2010 / 2011 (CLO3, C4)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 4

19. A student would like to prepare 250 mL of 0.25 mol L-1 lead (II) nitrate, Pb(NO3)2 solution. (20.70 g)
Calculate the mass of Pb(NO3)2 required to prepare the solution.
UPS 2015 / 2016 (CLO3, C4)

20. A 200 cm3 of perfume contains 28 cm3 of alcohol. What is the concentration of alcohol by volume in
this solution? (CLO3, C4)

(14.00%)

21. Pure acetic acid, CH3COOH, is a liquid with a density of 1.049 g mL-1. A 10.0 mL of pure acetic acids
is pipette into a 100 mL volumetric flask and distilled water is added to the mark. Calculate the

molarity of the solution produced. UPS 2013 / 2014 (CLO3, C4)

[Molar mass of CH3COOH = 60 g mol-1] (1.75 M)

HOUR : 5

22. An aqueous ammonia solution with a density of 0.898 g mL-1 contains 28.0% ammonia by mass.

Calculate the molarity of the solution. UPS 2006 / 2007 (CLO3, C4)
(14.79 M)

23. The density of an aqueous solution containing 10.0 % of ethanol, C2H5OH by mass is 0.984 g mL-1.
Calculate
a) the molality of the solution (2.42 molal)

b) its molarity (2.14M)

c) the volume of the solution that contains 0.125 mole of ethanol (0.058 L)

[ molar mass of ethanol, C2H5OH = 46.0 g mol-1] UPS 2008 / 2009 (CLO3, C4)

24. The density of 10.5 molal NaOH solution is 1.33 g mL– 1 at 20.0 °C. Calculate: (CLO3, C4)
a) the mole fraction of NaOH. (0.159)
b) the percentage by mass of NaOH.
c) the molarity of the solution. (29.58%)
(9.83 M)

25. Sodium carbonate, Na2CO3 dissolves in ethanol to give 2.5 M solution. Calculate the molality of the
solution if the density of the solution is 1.43 g mL-1. PSPM 2016 / 2017 (CLO3, C4)
(2.15 mol kg-1)

26. A 50.0 mL saturated solution of NaOH containing 52.0% NaOH by weight with a density of
1.48 g mL-1 is used to prepare a 0.100 M solution. Determine the initial concentration of the NaOH
solution and the amount of water required to prepare the 0.100 M NaOH solution.
PSPM 2006 / 2007 (CLO3, C4)
(19.24 M , 9.57 L @ 9570 mL)

HOUR : 6

27. Balance each of the following equations: (CLO3, C3)
a) NaOH(aq) + FeCl3(s) ⎯→ Fe(OH)3(s) + NaCl(aq)
b) C4H10(g) + O2(g) ⎯→ CO2(g) + H2O(l)
c) Fe(s) + H2O(l) ⎯→ Fe3O4(s) + H2(g)
d) Fe2O3(s) + HCl(aq) ⎯→ FeCl3(aq) + H2O(l)
e) Cr(OH)3(aq) + IO3−(aq) ⎯→ CrO32−(aq) + I−(aq) (acidic medium)
f) Cl2(aq) ⎯→ ClO4–(aq) + Cl–(aq) (basic medium)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 5

28. A solution containing I− ion was titrated in acidic medium with MnO4− ion to form I2 and Mn2+.
a) Write the balanced equation for the titration.

b) How many millilitres of a 0.206M I− solution are needed to reduce 22.5 ml of a 0.374M

MnO4−? (204.24 mL)

(CLO3, C4)

HOUR : 7

29. A reaction between 7.0 g of copper(II) oxide and 50 mL of 0.20 M nitric acid produces copper(II)

nitrate, Cu(NO3)2 and water. (CLO3, C4)

a) Define limiting reactant.

b) Write the balanced chemical equation for the above reaction
c) Determine the limiting reactant

d) Calculate the mass of excess reactant after the reaction (6.60g)

30. At room temperature, 255 g of copper (I) oxide, Cu2O react with 180 g of copper (I) sulphide Cu2S
according to the equation below,

2Cu2O + Cu2S 6Cu + SO2
Determine:

a) the limiting reactant. (38.07g)
b) the mass of the excess reactant remained at the end of the reaction.

(molar mass of Cu2O = 143.2 g mol-1 ; molar mass of Cu2S = 159.3 g mol-1)
UPS 2006 / 2007 (CLO3, C4)

31. In an experiment, 0.355 g of aluminium, Al reacts with 20.00 mL of 4.00 M hydrochloric acid, HCl

according to the following equation:

2Al (s) + 6HCl (aq) 2AlCl3 (aq) + 3H2 (g)

a) Determine the limiting reactant
b) If the percentage yield of hydrogen is 85.0%, calculate the actual mass of hydrogen obtained.

(0.0335 g)

UPS 2010 / 2011 (CLO3, C4)

32. In an experiment, 1.46g of magnesium is added into 160.00 mL of 0.50 mol L-1 hydrochloric acid.
The reaction involved is:
Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

a) Determine the limiting reactant for the above reaction
b) Calculate the percentage yield if 672.00 mL of hydrogen gas is obtained at STP. (75.00 %)

UPS 2014 / 2015 (CLO3, C4)

HOUR : 8

33. What is meant by percentage yield?

The combustion of potassium chloride, KCl produces potassium chlorate, KClO3 according to the
equation
2KCl (s) + 3O2 (g) 2KClO3 (s)
Calculate the mass of oxygen gas needed to produce 3.80 g of potassium chlorate if the percentage

yield is 86.0%

PSPM JUNE 2000 (CLO3, C4)
(1.73 g)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 6

34. A 72.0 g vanadium pentoxide, V2O5, reacts with excess aluminium, Al, at high temperature to produce
vanadium metal, V, and aluminium oxide, Al2O3. [Ar V : 51]
a) Write a chemical equation for the above reaction.

b) Calculate the mass of vanadium produced. (40.39 g)

UPS 2013 / 2014 (CLO3, C4)

35. Adipic acid, H2C6H8O4, is produced by a reaction between cyclohexane and excess oxygen. The
equation for the reaction is:

2C6H12 (l) + 5O2 (g) 2H2C6H8O4 (l) + 2H2O (l)
a) If 45.0 g of cyclohexane is used, calculate the theoretical yield of adipic acid (78.21 g)

b) Given the actual yield of adipic acid is 63.5 g, what is the percentage yield of adipic acid?

(81.19 %) UPS 2012 /2013 (CLO3, C4)

36. In an experiment, a student allowed benzene C6H6 to react with excess bromine, Br2 in an attempt to
prepare bromobenzene, C6H5Br. On the basis of the equation: (CLO3, C4)

C6H6 + Br2 ⎯→ C6H5Br + HBr
a) What is the maximum number of grams of C6H5Br the student could have hoped to obtain
from 15.00g of benzene? (30.17 g)

b) Calculate the percentage yield if 28.5g of C6H5Br is obtained. (94.46 %)

c) With the same percentage yield, how many grams of benzene C6H6 will have to start with to
obtain 10.0 g of C6H5Br. (5.27 g C6H6)

37. The neutralisation reaction between sulphuric acid and sodium hydroxide yields sodium sulphate and

water.
a) Write a balanced equation for the neutralisation.

b) Calculate the moles of sodium hydroxide needed to yield 0.080 mol of sodium sulphate.

(0.16 mol)

c) Calculate the mass of sulphuric acid needed for the reaction in (b). (7.85 g)
PSPM JUNE 2000 (CLO3, C4)

HOUR : 9

38. An analysis using mass spectrometer shows that copper consists of two natural occurring isotopes,
63Cu and 65Cu.The ratio of relative abundance for the two isotopes.

63 Cu = 2.235
65 Cu

Calculate the percentage abundance of each isotope. (69.09%, 30.91%)
PSPM 2002 /2003 (CLO3, C4)

39. A hydrate of potassium carbonate has the formula, K2CO3.xH2O. When 10.00 g of the hydrate was
heated, 7.95 g of anhydrous salt was left. Determine the value of x in the formula.
PSPM 2004 / 2005 (CLO3, C3)

40. a) A 25.0 mL of 0.050 M silver nitrate solution is mixed with 25.0 mL of 0.050M of calcium

bromide solution to give 0.105 g of solid silver bromide. (CLO3, C4)

i) write the balanced chemical equation for this reaction
ii) determine the limiting reactant

iii) calculate the percentage yield of silver bromide (44.73 %)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 7

b) An organic compound contains only carbon, hydrogen and oxygen with a mass composition
of 41.40% C, 3.47 % H and 55.13% O. If 0.05 mol of this compound weighs 5.80 g, determine

its

i) its empirical formula

ii) molecular formula PSPM 2017 / 2018 (CLO3, C3)

41. The following is the mass spectrum of zirconium is shown in FIGURE 3. Calculate the average atomic

mass of zirconium. (CLO3, C4)

relative 52.0
abundance, %

14.0 13.0
9.0 12.0

90 91 92 93 94 mass (u) (91.27 u)
FIGURE 3

42. Copper has an average atomic mass of 63.546 a.m.u. It exists as two natural isotopes, which are

63Cu with a mass of 62.940 and 65Cu with a mass of 64.928. Determine the percentages of the two

isotopes in naturally occurring copper. PSPM DK015 2012 / 2013 (CLO3, C4)

(69.52%, 30.48%)

HOUR : 10

43. a) Consider the following reaction:

2NO(g) + 2CO(g) N2(g) + 2CO2(g)
If 300.00 g of CO has reacted, calculate the mass percentage, % w/w of CO2 in the mixture
of the product. (75.86 %)

b) A 30.00 mL of 0.025 M sodium dichromate, Na2Cr2O7, solution is titrated with iron (II)
sulphate, Fe2SO4 solution in acidic condition, according to the following reaction:
Cr2O72− + Fe2+ Cr3+ + Fe3+

The titration requires 40.00 mL of Fe2SO4 solution to reach the end point.
i) Balance the redox equation.
ii) Calculate the mass of Na2Cr2O7 needed to prepare a 0.025 M solution in a 50 mL
volumetric flask. (0.33 g)

iii) Determine the molarity of the Fe2+ solution. (0.11 M)

PSPM 2014 / 2015 (CLO3, C4)

44. Compound Q contains carbon, hydrogen and nitrogen. Combustion of 0.250 g of Q produces
0.344 g of water, H2O, and 0.558 g of carbon dioxide, CO2. Determine
a) the empirical formula of Q,
b) the molar mass of Q if the molecular formula is the same as the empirical formula
(59.0 g mol-1)
PSPM 2015 / 2016 (CLO3, C3)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 8

45. The following redox reaction occurs in acidic condition:
Zn + NO3- → Zn2+ + NH4+
a) Balance the redox equation using ion-electron method

b) A 4.0g impure sample of zinc reacted completely with 25.0 mL if 0.5M HNO3 solution.
Calculate the percentage purity of the zinc sample (81.75 %)

PSPM 2016 / 2017 (CLO3, C4)

46. Balance each of the following equations: (CLO3, C3)
a) SO32− + MnO4− ⎯→ SO42− + Mn2+ (acidic medium)
b) ClO2 ⎯→ ClO3− + Cl− (basic medium)

HOUR :11

47. a) FIGURE 5 shows the mass spectrum for copper, Cu atom which has been identified to have
two isotopes.

62.9298 64.9278

Relative
Abundance

62 63 64 65 66

Mass / charge

FIGURE 5

Using the information given in FIGURE 5, calculate the abundance of each isotope for Cu.
(66.46%, 33.54%)

b) Urea, (NH2)2CO is used as fertilizer and in animal feed. It is prepared by reacting ammonia ‘
and carbon dioxide as shown:
48. a)
b) 2NH3 (g) + CO2(g) (NH2)2CO (s) + H2O(l)
In a urea production 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. (1124.46 g)

PSPM 2008 / 2009 (CLO3, C4)

Saline solution is prepared by dissolving 9.0 gram of NaCI in deionized water in a 500 mL

volumetric flask. Calculate the molarity of the solution. (0.31 M)

Nitric oxide, NO reacts with oxygen to produce nitrogen dioxide, NO2:
2NO(g) + O2(g) 2NO2(g)
In an experiment, 0.530 mol of nitric oxide is mixed with 0.300 mol oxygen. Calculate the

volume of NO2 produced at STP. (11.87 L)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 9

c) Freon-12, CCI2F2 is used in various manufacturing industries. It is produced from the reaction
of carbon tetrachloride, CCI4 with antimony trifluoride, SbF3:
3CCI4 + 2SbF3 3CCI2F2 + 2SbCI3
If 130.0 g of CCI4 is mixed with 95.0 g of SbF3, calculate
i) the amount (in grams) of CCI2F2 obtained. (96.44 g)
ii) the amount of excess reactant after the reaction is completed. (7.26 g)

PSPM 2011 / 2012 (CLO3, C4)

49. a) Hydrogen reacts with oxygen to produce water as in the reaction equation below. Assume
that before the reaction takes place, there is 20 g H2 and 224 g O2 gas.
2H2(g) + O2(g) 2H2O(g)
i) Determine the limiting reagent in this reaction. Show your calculation.

ii) Determine the quantity in moles of H2 and O2 consumed in the reaction.
iii) Calculate the mass of H2O produced at the end of the reaction.
iv) Calculate the mass of the excess reagent left after the reaction has completed.

b) The following redox reaction occurs in an acidic solution:
MnO4- + C2O42- Mn2+ + CO2
i) State the changes in oxidation numbers of Mn and C.

ii) Complete and balance the reaction equation.

PSPM DK015 2011 / 2012 (CLO3, C4)

50. In a titration between an acidic solution of Fe2+ and K2Cr2O7 solution, the Fe2+ ions were oxidised to
Fe3+ while the dichromate ions Cr2O72− were reduced to Cr3+.

25.00 mL of the Fe2+ solution was titrated against 31.00 mL of 1.85 10–2 M K2Cr2O7 solution.

a) Write a balanced equation for the titration

b) Calculate the concentration of the Fe2+ solution used (0.14 M)

PSPM 2001 / 2002 (CLO3, C4)

HOUR : 12

51. a) A sample of chlorine consists of two isotopes 35 Cl and 37 Cl . The relative atomic mass of
b) 17 17

chlorine is 35.5. Determine the percentage composition of each isotope in the sample.

(25%,75%)

An impure solid sample of iron is reacted with an excess of hydrochloric acid,HCl, to form

an aqueous 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 0.274 g of the impure iron is reacted with an excess of hydrochloric acid, HCl,

an amount of 8.54 × 10-3 g of H2 gas is evolved. Calculate the percentage of iron in
the sample. (87.23 %)

PSPM 2010 / 2011 (CLO3, C4)

52. A solution of 95.0 % sulphuric acid, H2SO4 by mass has a density of 1.84 g mL –1.
Calculate

a) the molarity of the H2SO4 solution (17.83 M)

b) the volume of the acid needed to prepare 1.00 L of 0.0800 M H2SO4 solution.
[Mr H2SO4 = 98.07] (4.49 × 10-3 L)
PSPM 2003 / 2004 (CLO3, C4)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 10

53. a) Bromine has proton number of 35. FIGURE 6 shows a mass spectrum of bromine.

% abundance 51
49

79 81 m/e

FIGURE 6 (79.98)
i) Write the notations for all isotopes of bromine.

ii) Calculate the relative atomic mass of bromine.

b) A reagent bottle contains a stock solution of 0.90% by mass of sodium chloride, NaCl. The

density of solution is 1.00 g cm-3. Calculate:

i) the mole fraction of NaCl. (0.0028)

ii) the molality of NaCl solution. (0.16 molal)
iii) the volume of the stock solution required to prepare 100 mL of 0.01 M NaCl solution.

(6.49 mL)

c) Silicon tetrachloride, SiCl4 can be prepared by heating silicon in excess chlorine gas.
Si (s) + 2Cl2(g) SiCl4(l)
i) Calculate the mass of silicon needed to produce 400 g of SiCl4, if the percentage
yield is 42.5%. (155.48 g)

ii) If 15 mol of chlorine is used, determine the amount (mole) of unreacted chlorine.

(3.93 mol)

PSPM 2018 / 2019 (CLO3, C4)

CHEMISTRY UNIT KMNS, SESSION 2022 / 2023 11