T3 MOLE CONCEPT_QUESTIONS

CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

CHAPTER 3
MOLE CONCEPT

Face-to-Face Non Face-to-Face
6 6

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

3.0 MOLE CONCEPT

3.1 Avogadro number and molar (a) Define mole in terms of mass of carbon-12 and Avogadro’s

mass constant(NA)
(b) Relate Avogadro’s number with molar mass and molar volume

of gas at room temperature and Standard Temperature and

Pressure (STP).

3.2 Empirical and molecular (a) Define the terms empirical and molecular formulae.
formula (b) Determine empirical and molecular formulae from mass

composition and combustion data.

3.3 Concentration (a) Define :
i) molarity;
ii) density; and

iii) % by mass
(b) Perform calculations on molarity and % by mass

* include dilution

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

TUTORIAL 3
MOLE CONCEPT

OBJECTIVE QUESTIONS:

HOUR 6

1. What is the number of oxide ions in 50.0 g of aluminium oxide?

A. 50 x 2 x NA
B. 15002x 3 x NA
15002x 3
C. 5 x NA

D. 50 x 23x NA (CLO 1, C1)

2. What is the volume of oxygen gas at s.t.p. which contains 1.5 x 1024 oxygen atoms?
A. 14 dm3

B. 28 dm3

C. 56 dm3

D. 70 dm3 (CLO 1, C1)

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

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

SUBJECTIVE QUESTIONS:

HOUR 1

1. Define mole in terms of: (CLO 1, C1)
(a) the mass of C-12 (CLO 1, C3)
(b) Avogadro constant, NA (CLO 1, C3)

2. Calculate the number of moles of:
(a) Mg atoms in 10.50 g magnesium.
(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

HOUR 2

4. Complete the following table for citric acid, C6H8O7

No. of grams No. of moles No. of molecules No. of O atoms
5.55 x 1019
0.1364

1.248

4.32 x 1022

(CLO 1, C 3)

5. Calculate the number of sulphur atoms which have the same mass as 3.6 x 1023 copper atoms.
(CLO 4, C3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

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 4, 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 4, C3)

8. A sample of carbon dioxide has a volume of 56.0 cm3 at s.t.p. Calculate the number of: (CLO 4, C3)
(a) moles of gas molecules
(b) molecules
(c) oxygen atom in the sample

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 4, 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 4, 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 4, C3)

HOUR 4 (CLO 1, C1)
(CLO 4, 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) 0.1M NaCl MATRIKULASI KPM
(b) 0.2M Na2SO4 SISTEM EMPAT SEMESTER (S4S)
(c) 2.0M HNO3
(d) 0.5 M Fe2(SO4)3 (CLO 4, C3)
(e) 60.0 g L-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 4, 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 4, C3)

17. The density of an aqueous solution containing 10.0 % of ethanol, C2H5OH by mass is 0.984 g/mL.
Calculate its molarity.
ADDITIONAL QUESTIONS

18. At 25 ⁰C and 1 atm, 5.0 mol of chlorine gas occupy container X. Determine (CLO 4, 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 4, 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 4, 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 4, C3)

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