T2 MOLE CONCEPT_QUESTIONS

CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

CHAPTER 2

MOLE CONCEPT

Face-to-Face Non Face-to-Face
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At the end of this topic, the student should be able to:

2.0 MOLE CONCEPT

2.1 Mole (a) Define mole in terms of mass of carbon-12 and Avogadro’s constant
(NA).
(b) Relate Avogadro’s number with molar mass and molar volume of gas at
room condition and standard temperature pressure (STP)

2.2 Empirical and (a) Define the terms empirical and molecular formulae.
molecular formulae (b) Determine empirical and molecular formulae from mass composition
and combustion data.

2.3 Concentration (a) Describe:

i. molarity
ii. percentage by mass
(b) Perform calculations on molarity and percentage by mass.
*include dilution
*use density as conversion factor

2.4 Chemical (a) Identify the oxidation number of an element in a chemical formula.
Equation (b) Write and balance chemical equation by:

i. inspection method; and
ii. ion-electron method for redox reaction.
2.5 Stoichiometry (a) Calculate the amount of reactant and product from a balanced

chemical equation.
Calculation involve:
i. reacting masses and moles;
ii. volume of gases at room condition and STP; and

iii. volume and concentration of solutions.
(Experiment 2: Standard Solution and Determination of the Concentration of
Acid solution)
(Experiment 3: Quantitative Analysis of Baking Soda)
(b) Define:

i. limiting reactant;
ii. theoretical yield;

iv. actual yield; and
v. percentage yield.
(c) Perform calculation involving limiting reactant and percentage yield.

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

TUTORIAL 2
MOLE CONCEPT

OBJECTIVE QUESTIONS:

HOUR 15

1. What is the number of oxide ions in 50.0 g of aluminium oxide?
A. 50 x 2 x NA

B. 50 x 3 x NA

102 3
50 x 5
C. x NA
102
3x
D. 50 x NA (CLO 1, C1)
2 (CLO 1, C1)

2. What is the volume of oxygen gas at STP which contains 1.5 x 1024 oxygen atoms?
A. 14 dm3
B. 28 dm3
C. 56 dm3
D. 70 dm3

3. On heating, 0.33 mol of lead reacts with 0.33 mol of oxygen gas. What is the empirical formula of the oxide of

lead?
A. PbO
B. PbO2
C. Pb2O3
D. Pb3O4 (CLO 1, C1)

4. A 100 g of solution contains 35.0 g of HBr and has the density of 1.30 gmL-1. Calculate the molarity of this solution.
A. 6.00 M

B. 5.00 M

C. 5.63 M

D. 5.80 M (CLO 1, C2)

5. How many grams of NaOH are present in 2000 mL of 0.1 M NaOH solution? (CLO 1, C2)
(Mr NaOH = 40 gmol-1)
A. 4 g
B. 8 g
C. 40 g
D. 80 g

6. In chemistry, stoichiometry is used to interpret a chemical equation. Select the statement which is
CORRECT about stoichiometry.
A. The qualitative study of reactants and products in a chemical reaction.
B. The quantitative study of reactants and products in a chemical reaction.
C. Number of mole of the reactants and products in a chemical equation.
D. Ratio of number of mole of the reactants and products in a chemical equation.
(CLO 1, C1)

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CHEMISTRY DK014

MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

7. Select the statement which explain why chemical equations need to be balanced.
A. Because total number of particles of the reactants is the same with total number of particles of
the products.
B. Because total number of mole of the reactants is the same with total number of mole of the
products.
C. Because a chemical equation follows the law of conservation of mass.
D. Because a chemical equation follows the law of conservation of energy.
(CLO 1, C2)

8. Select the FALSE statement about 1 mole of oxygen gas. (CLO 1, C2)
A. It contains 32.0 g of particles.

B. It contains 6.02 x 1023 molecules.
C. The volume of the gas is 24 dm3 at R.T.P.
D. The pressure of the gas is 1 atm.

9. Identify the oxidation state of sulphur in S2O82- ? C. +7 (CLO 1, C2)
A. -2 D. +8
B. +4

10. Select from the following pairs which gives INCORRECT oxidation number for the underlined element.
A. BFerOO4- (+7) C. MIOg3(-OH)2 (+3)
B. (+2) D. (+5) (CLO 1, C2)

11. Select from the following which is NOT TRUE about oxidation number of an element in a chemical
formula.
A. Fluorine oxidation number is a positive number when combine with oxygen
B. Oxygen oxidation number is -2 in most of its compound.
C. Hydrogen oxidation number is +1 in metal hydrides but -1 in its compound
D. Monatomic ion, the oxidation number is equal to the charge on the ion.
(CLO 1, C1)

12. Identify the balance chemical equation.
A. NH3 + CuO → Cu + N2 + H2O
B. 2NH3 + CuO → Cu + N2 + 3H2O
C. 2NH3 + 3CuO → 3Cu + N2 + 3H2O
D. 2NH3 + 3CuO → Cu + N2 + 3H2O
(CLO 1, C2)

13. Select the CORRECT statement about oxidation reaction.
A. Increase in oxidation number.
B. Acts as oxidant
C. The substance accept one or more proton(s)
D. The substance accept one or more electron(s)

(CLO 1, C1)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

14. Identify how many moles of H2O will be formed when 0.25 mol of C2H5OH burns in oxygen.

Given the equation

C2H5OH + 3O2 2CO2 + 3H2O

A. 0.075 mol

B. 0.75 mol
C. 0.025 mol

D. 0.25 mol

(CLO 1, C2)

15. Select from the following which is TRUE about limiting reactant.

A. A limiting reactant remains excess at the end of a chemical reaction.
B. A limiting reactant has the smallest number of mole based on the balanced equation.

C. A limiting reactant is used up at the end of a chemical reaction.

D. A limiting reactant has the largest number of mole based on the balanced equation.

(CLO 1, C1)

16. If the percentage yield is equal to 100%, Select the TRUE statement
A. The actual yield is greater than the theoretical yield.
B. The actual yield is equal to the theoretical yield.
C. The actual yield is less than the theoretical yield.
D. There was no limiting reactant.

(CLO 1, C2)

17. Select the information which must be known in order to determine the limiting reactant in a chemical

reaction
A. amount of product formed.
B. available amount of each reactant.
C. speed of the reaction.
D. available amount of one of the reactants.

(CLO 1, C2)
18. Select the CORRECT statement about actual yield.

A. less than the theoretical yield
B. greater than the theoretical yield.
C. equal to the theoretical yield.
D. greater than the percentage yield.

(CLO 1, C1)

19. A propane grill on a backyard patio is left burning for too long and eventually goes out. Identify from the
following which is the limiting reagent.
A. propane
B. water vapour
C. oxygen gas
D. carbon dioxide gas
(CLO 1, C1)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

20. Select the CORRECT statement about theoretical yield.
A. The amount of product formed based on the amount of limiting reactant.
B. less than the actual yield.
C. equal to the amount of limiting reactant
D. The amount of product formed based on amount of excess reactant.

(CLO 1, C1)

SUBJECTIVE QUESTIONS: HOUR 1

1. Define mole in terms of: (CLO 1, C1)
(a) the mass of C-12 (CLO 1, C3)
(b) Avogadro’s constant, NA (CLO 1, C3)
No. of O atoms
2. Calculate the number of moles of:
(a) Mg atoms in 10.50 g magnesium. 5.55 x 1019
(b) 9.54 g of sulphur dioxide, SO2.
(c) Sc atoms in 5.00 g of scandium(III) oxide, Sc2O3.
(d) hydrogen atoms in 85.16 g of ammonia, NH3.
(e) Al3+ ions in 2.5 mol aluminium sulphate, Al2(SO4)3.

3. How many moles of phosphorus atoms in
(a) 3.1 g phosphorus
(b) 31 phosphorus atoms
(c) 3.1 x 1023 phosphorus atoms
(d) 3.1 g P4
(e)
HOUR 2

4. Complete the following table for citric acid, C6H8O7

No. of grams No. of moles No. of molecules

0.1364

1.248

4.32 x 1022

(CLO 1, C 3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

5. Calculate the number of sulphur atoms which have the same mass as 3.6 x 1023 copper atoms.
(CLO 2, C3)

6. A sample of element A contains 1.58 x 1019 atoms and its mass being 1.05 mg. Calculate the relative atomic mass
of the element. (CLO 2, C3)

7. A mixture is made up of 1.65 x 1021 X molecules and 1.85 x 1021Y molecules. The mass of the mixture is 0.688 g.

If the relative molecular mass of Y is 42.0, what is the relative molecular mass of X?

(CLO 2, C3)

8. A sample of carbon dioxide has a volume of 56.0 cm3 at STP. Calculate the number of:
(a) moles of gas molecules
(b) molecules

(c) oxygen atom in the sample (CLO 2, C3)

HOUR 3

9. (a) Define empirical formula and molecular formula. (CLO 1, C1)

(b) Determine the empirical formula for substances which have the following percentage mass composition:
(i) 15.8% Al, 28.1% S, 56.1% O.
(ii) 16.3% Mg, 18.9% N, 64.7% O.
(iii) 14.3% Na, 10.0% S, 19.9% O, 55.5% water. (CLO 3, C3)

10. A compound consisting of 40.00% mass C, 6.71% mass H and 53.35% mass O has a relative molecular mass of
120. Determine the:
(a) empirical formula.
(b) molecular formula of the compound. (CLO 3, C3)

11. 1.367 g sample of a substance was burned in air to produce 3.002 g CO2 and 1.640 g water. If the sample contains

only C, H and O, determine the empirical formula. (CLO 3, C3)

HOUR 4 (CLO 1, C1)
(CLO 3, C3)
12. Define molarity.

Calculate the molarity of the following solutions:
(a) 98 g sulphuric acid, H2SO4 in 1 L solution.
(b) 5.85 g sodium chloride, NaCl in 250.0 mL solution.
(c) 10.6 g anhydrous sodium carbonate, Na2CO3 in 100 mL solution.

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13. Calculate the molarity of each ion in the following solutions: CHEMISTRY DK014
(a) 0.1 M NaCl MATRIKULASI KPM
(b) 0.2 M Na2SO4 SISTEM EMPAT SEMESTER (SES)
(c) 2.0 M HNO3
(d) 0.5 M Fe2(SO4)3 (CLO 3, C3)
(e) 60.0 gL-1 NH4OH

HOUR 5

14. How many moles of solute are present in the following solutions? (CLO 1, C2)
(a) 50.0 mL of 0.1 M NaOH
(b) 25.0 mL of 1.0 M HCl
(c) 550.0 mL of 1.5 M Na2CO3

15. Calculate the molarity of Na2CO3 solution which contains 2.0 x 1021 Na+ ions in 1.0L of solution.
(CLO 3, C3)

16. Calculate the mass of sodium chloride, NaCl, that must be dissolved in 1 kg of water to give 1.5 M solution.
(CLO 3, C3)

17. The density of an aqueous solution containing 10.0 % of ethanol, C2H5OH by mass is 0.984 g/mL.
Calculate its molarity. (CLO 3, C3)

HOUR 6

18. At 25 ⁰C and 1 atm, 5.0 mol of chlorine gas occupy container X. Determine (CLO 3, C3)
(a) the volume of container X.
(b) the mass of ammonium gas, NH3 that occupies container X at the same
temperature and pressure.

19. Mannose is a type of sugar that consists of C, H and O and its relative molecular mass is 180. If 2.36 g sample of
mannose contains 0.9444 carbon and 0.158 g hydrogen, calculate the molecular formula.
(CLO 3, C3)

20. Gasoline is a typical hydrocarbon primarily used as a fuel in internal combustion engines of cars and motorcycles.
It contains 84.21% carbon and has a molar mass of 114 gmol-1. Determine the molecular formula of gasoline.
(CLO 3, C3)

21. Saline solution is prepared by dissolving 9.0 gram of NaCI in deionized water in a 500mL volumetric flask. Calculate

the molarity of the solution. (CLO 3, C3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

HOUR 7

22. Determine the oxidation number of the underlined elements. (CLO 1, C2)

(a) MnCO3 (f) KNO3
(b) KMnO4 (g) KClO3
(c) MnO2 (h) Na2SO4
(d) SnF4 (i) NaClO4
(e) K2Cr2O7

23. Assign oxidation numbers to all the elements in the following species. (CLO 1, C2)
(a) Li2O
(b) HNO3
(c) Cr2O72−

24. Write the balanced chemical equations for the following reactions. (CLO 2, C3)

(a) Burning carbon in oxygen to form carbon dioxide.
(b) Burning carbon in limited supply of oxygen to form carbon monoxide.
(c) Burning aluminium in chlorine gas to form aluminium chloride.
(d) Heating solid potassium chlorate to form solid potassium chloride and oxygen gas.
(e) Reacting aluminium with aqueous hydrochloric acid to produce aqueous aluminium chloride and hydrogen
gas.

(f) Burning hydrogen sulphide gas in air to form gaseous sulphur dioxide and steam.

HOUR 8 (CLO 2, C3)
(CLO 2, C3)
25. Balance the following equations.
(a) Fe + O2 → Fe2O3
(b) Fe2O3 + HCl → FeCl3 + H2O
(c) AgNO3 + Na2CrO4 → Ag2CrO4 + NaNO3
(d) C2H6 + O2 → CO2 + H2O
(e) NH3 + CuO → Cu + N2 + H2O

26. Balance the following equations by the ion-electron method.
(a) Cr2O72− + Cl− → Cr3+ + Cl2 (acidic medium)
(b) Cu + NO3− → Cu2+ + NO (acidic medium)
(c) MnO4− + C2O4 2− → MnO2 + CO2 (basic medium)
(d) CrO42− + SO32− → Cr(OH)3 + SO42− (basic medium)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

HOUR 9

27. Like many metals, aluminium reacts with a halogen to give a metal halide.
2Al + 3Br2 → Al2Br6

Determine, (CLO 2, C3)
(a) number of mol Al2Br6 produced if 2.0 moles Br2 used in the reaction. (CLO 2, C3)
(b) number of mol of Br2 reacted with 3.48 g of Al. (CLO 2, C3)
(c) volume of bromine gas need at STP to produced 53.34 g of Al2Br6.

28. Calculate the number of moles of carbon dioxide, CO2 formed when 0.28 mol of ethanol, C2H5OH is burned in
excess oxygen to form carbon dioxide and water. (CLO 2, C3)

HOUR 10

29. 63.0 L of carbon monoxide, measured at STP was used in a reaction with iron (III) oxide. Calculate the mass of
the iron produced at the end of the reaction. The equation for the reaction is

Fe2O3 (s) + 3CO (g)  2Fe (s) + 3CO2 (s). (CLO 3, C3)

30. Potassium oxalate, K2C2O4 reacts with acidified KMnO4 solution to give Mn2+ ion, CO2, and H2O. In a redox titration,
50.0 mL of 0.100 M K2C2O4 solution is titrated with 0.200 M KMnO4 solution.
C2O42− + MnO4− → Mn2+ + CO2 + H2O

(a) Write and balance the redox equation for the above reaction. (CLO 2, C3)
(b) Determine the volume of the KMnO4 solution that will completely oxidise the oxalate ion. (CLO 2, C3)

HOUR 11 (CLO 1, C1)
(CLO 2, C3)
31. (a) Define limiting reactant.
(b) Zinc reacts with hydrochloric acid according to the equation below, (CLO 2, C3)
Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g) (CLO 2, C3)
(CLO 2, C3)
If 0.05 mol of zinc was added to 0.075 mol of hydrochloric acid,
i. determine the limiting reactant.
ii. calculate the moles of zinc chloride formed.

32. 10.0 g of Mg is added to a beaker containing 0.18 mol of HCl to form MgCl2 and H2 gas.
(a) Write a balance chemical equation
(b) Determine the limiting reactant.
(c) Calculate the mass of H2 produced.

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

HOUR 12

33. 10.0 g of calcium carbonate, CaCO3 reacted with a 50.0 mL hydrochloric acid solution with a molarity of 0.20 M to
form carbon dioxide, CO2, calcium chloride, CaCl2 and water, H2O.
(a) Write the balance chemical equation for the reaction. (CLO 2, C3)
(b) Determine the limiting reactant. (CLO 2, C3)
(c) Calculate the volume of CO2 produced at STP. (CLO 2, C3)
(d) Calculate the mass of excess reactant remained after the reaction is completed. (CLO 2, C3)

34. Potassium superoxide, KO2 reacts with water to produce potassium hydroxide, KOH, and oxygen according to the
following equation.
4KO2 (s) + 2H2O (l)  4KOH (aq) + 3O2 (g)

(a) If 0.30 mol KO2 reacts with 0.20 mol H2O, which is the limiting reactant. (CLO 2, C3)
(b) Determine the volume of O2 produced at STP. (CLO 2, C3)

35. Zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen gas. 150 g of zinc was dropped into a
beaker containing HCl of unknown concentration. After the reaction had ceased, 50 g of the unreacted zinc
remained in the beaker.

(a) Write a balanced chemical equation for the reaction. (CLO 2, C3)
(b) Which is the limiting reactant? (CLO 2, C3)
Explain your answer. (CLO 2, C3)
(c) Calculate the moles of hydrochloric acid reacted. (CLO 2, C3)
(d) How many moles of hydrogen gas were produced? (CLO 2, C3)

(e) If the experiment were performed at STP, what would be the volume of the H2 gas produced? (CLO 2, C3)

HOUR 13

36. Carbon tetrachloride, CCl4 was prepared by reacting 50.0 g of carbon disulphide with 50.0 g of chlorine according
to the following reaction,
CS2 + 3Cl2 → CCl4 + S2Cl2

(a) Determine the limiting reactant. (CLO 2, C3)
(b) Calculate the mass of CCl4 formed. (CLO 2, C3)
(c) Calculate the percentage yield if 35.0 g of CCl4 was obtained from the experiment. (CLO 2, C3)

37. The following questions are based on the reaction given below.
2Cu2O(s) + Cu2S(s)  6Cu (s) + SO2(g)

200 g of Cu2O is heated together with 150 g of Cu2S. Determine, (CLO 2, C3)
(a) the limiting reactant. (CLO 2, C3)
(b) the volume of SO2 formed at S.T.P. (CLO 2, C3)
(c) the mass of excess reactant remained at the end of the reaction.

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

38. (a) Define theoretical yield, actual yield and percentage yield. (CLO 1,C1)
(b) Aluminium reacts with bromine gas to form aluminium bromide, AlBr3.
i. Write the balanced chemical equation. (CLO 2, C3)

ii. Determine the limiting reactant if 30.0 g of Al reacted with 100.0 g of Br2. (CLO 2, C3)
iii. Calculate the mass of the product at the end of the reaction. (CLO 2, C3)
iv. What is the percentage yield for the reaction if only 55.0 g of AlBr3 were actually recovered at the end
of the reaction? (CLO 2, C3)

HOUR 14

39. When a solution, containing silver ion, Ag+, has been treated with excess chloride ions, Cl-, 0.1234 g of solid AgCl
was obtained. Assume the percentage yield to be 98.7%.
(a) Write the balance equation for the reaction. (CLO 2, C3)
(b) Calculate the theoretical yield of AgCl. (CLO 2, C3)
(c) How many grams of silver ions were present in the solution? (CLO 2, C3)

40. During the extraction of iron, the hematite (Fe2O3) was reduced to iron metal by carbon
monoxide according to the following equation (not yet balanced),
Fe2O3 + CO  Fe + CO2

(a) Balance the equation. (CLO 2, C3)
(b) Determine the limiting reactant if 300 g of hematite and 60 g of CO are used in the
extraction.
(CLO 2, C3)

(c) Calculate the mass of iron produced and the percentage yield if the mass of iron extracted is 70g.
(CLO 2, C3)
(d) Determine the mass of the excess reactant remained after the reaction had ceased. (CLO 2, C3)

41. Hydrogen sulphide gas burn in air to form gaseous sulphur dioxide and steam. Write the complete

balanced chemical equations for the reaction. (CLO 2, C3)

42. Reaction of acidified KMnO4 solution with Potassium oxalate, K2C2O4 produced Mn2+ ion, CO2 and
H2O. In a redox titration, 50.0 mL of 0.100 M K2C2O4 solution was titrated with KMnO4 solution.
C2O42- + MnO4- → Mn2+ + CO2 + H2O

(a) Determine the oxidation number of the underline elements. (CLO 1, C2)

(b) i. Write half equations and balance the redox equation for the above reaction.

ii. balance the redox equation for the above reaction. (CLO 2, C3)
(c) KMnO4 solution with concentration 0.500 M was completely oxidised the oxalate ion, determine

the volume of KMnO4 solution required for the reaction. (CLO 2, C3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (SES)

43. In an experiment, 0.4115 mol of Mg is allowed to react with 0.18 mol of HCl to form MgCl2 and H2
gas by the following equation:
Mg (s) + 2HCl (aq)  MgCl2(aq) + H2(g)

(a) Define limiting reactant. (CLO 1, C1)
(b) Determine the limiting reactant. (CLO 2, C3)

44. During the extraction of iron, 300g of Fe2O3 was reduced to iron metal by exactly
3.60 mol of carbon monoxide according to the following reaction:

Fe2O3 + 3CO  2Fe + 3CO2
Calculate the mass of iron produced and the percentage yield if 82g of iron is obtained.

(CLO 2, C3)

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