T4 CHEMICAL EQUATION & STOICHIOMETRY_QUESTIONS

CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

CHAPTER 4

CHEMICAL EQUATION AND STOICHIOMETRY

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

4.0 CHEMICAL EQUATION AND STOICHIOMETRY

4.1 Chemical (a) Determine the oxidation number of an element in a chemical formula.
Equation (b) Write and balance:

i. chemical equation by inspection method; and
ii. redox equation by ion-electron method.

4.2 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;

iii. actual yield; and

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

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

TUTORIAL 4
CHEMICAL EQUATION AND STOICHIOMETRY

OBJECTIVE QUESTIONS:

HOUR 9

1. In chemistry, stoichiometry is used to interpret a chemical equation. What is ‘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 4, C1)

2. 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 4, C2)

3. Which statement is FALSE about 1 mole of oxygen gas?
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.

(CLO 4, C2)

4. What is the oxidation state of sulphur in S2O82- ? C. +7
A. -2 D. +8
B. +4

(CLO 4, C2)

5. Which of the following pairs gives incorrect oxidation number for the underlined element?
A. FBerOO4- (+7) C. MIOg3(-OH)2 (+3)
B. (+2) D. (+5) (CLO 4, C2)

6. Which of the following statement is NOT TRUE?
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 4, C1)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

7. Choose the balance chemical equation. (CLO 4, C2)
A. NH3 + CuO → Cu + N2 + H2O
B. 2NH3 + CuO → Cu + N2 + 3H2O
C. 2NH3 + 3CuO → 3Cu + N2 + 3H2O
D. 2NH3 + 3CuO → Cu + N2 + 3H2O

8. Choose 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 4, C1)

9. 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 4, C2)

10. Which of the following statement is TRUE about a ‘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 4, C1)

11. If the percentage yield is equal to 100%, which of the following statements is TRUE?
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 4, C2)

12. To determine the limiting reactant in a chemical reaction, which of the following information must be
known?
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 4, C2)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

13. The actual yield of a chemical reaction is generally…
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 4, C1)

14. A propane grill on a backyard patio is left burning for too long and eventually goes out. Which of the

following chemicals is the limiting reagent? C. oxygen gas
A. propane

B. water vapour D. carbon dioxide gas

(CLO 4, C1)

SUBJECTIVE QUESTIONS:

HOUR 1

1. Determine the oxidation number of the underlined elements. (CLO 4, C2)

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

2. Assign oxidation numbers to all the elements in the following species. (CLO 4, C2)
(a) Li2O
(b) HNO3
(c) Cr2O72−

3. Write the balanced chemical equations for the following reactions. (CLO 4, 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.

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

HOUR 2

4. Balance the following equations. (CLO 4, C2)
(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

5. Balance the following equations by the ion-electron method. (CLO 4, C3)
(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)

HOUR 3

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

Determine, (CLO 4, C4)
(a) number of mol Al2Br6 produced if 2.0 moles Br2 used in the reaction. (CLO 4, C4)
(b) number of mol of Br2 reacted with 3.48 g of Al. (CLO 4, C4)
(c) volume of bromine gas need at STP to produced 53.34 g of Al2Br6.

7. 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 4, C4)

HOUR 4

8. 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 4, C4)

9. 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 4, C3)
(b) Determine the volume of the KMnO4 solution that will completely oxidise the oxalate ion.
(CLO 4, C3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

HOUR 5

10. (a) Define limiting reactant. (CLO 4, C1)
(b) Zinc reacts with hydrochloric acid according to the equation below; (CLO 4, C3)
Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)

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.

11. 10.0 g of Mg is added to a beaker containing 0.18 mol of HCl to form MgCl2 and H2 gas. (CLO 4, C3)
(a) Write a balance chemical equation (CLO 4, C3)
(b) Determine the limiting reactant. (CLO 4, C3)
(c) Calculate the mass of H2 produced.

HOUR 6

12. 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 4, C3)

(b) Determine the limiting reactant. (CLO 4, C3)
(c) Calculate the volume of CO2 produced at STP (CLO 4, C3)

(d) Calculate the mass of excess reactant remained after the reaction is completed. (CLO 4, C3)

13. 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 4, C3)
(b) Determine the volume of O2 produced at STP. (CLO 4, C3)

14. 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 4, C3)

(b) Which is the limiting reactant? (CLO 4, C3)
Explain your answer. (CLO 1, C2)

(c) Calculate the moles of hydrochloric acid reacted. (CLO 4, C3)

(d) How many moles of hydrogen gas were produced? (CLO 4, C3)

(e) If the experiment were performed at STP, what would be the volume of the H2 gas produced?
(CLO 4, C3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

HOUR 7

15. 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.
(b) Calculate the mass of CCl4 formed.
(c) Calculate the percentage yield if 35.0 g of CCl4 was obtained from the experiment. (CLO 4, C3)

16. The following questions are based on the reaction given below. (CLO 4, C3)

2Cu2O(s) + Cu2S(s) → 6Cu (s) + SO2(g)
200 g of Cu2O is heated together with 150 g of Cu2S. Determine,
(a) the limiting reactant.
(b) the volume of SO2 formed at S.T.P.
(c) the mass of excess reactant remained at the end of the reaction.

17. (a) Define theoretical yield, actual yield and percentage yield. (CLO 4,C1)

(b) Aluminium reacts with bromine gas to form aluminium bromide, AlBr3. (CLO 4, C3)
i. Write the balanced chemical equation.

ii. Determine the limiting reactant if 30.0 g of Al reacted with 100.0 g of Br2. (CLO 4, C3)

iii. Calculate the mass of the product at the end of the reaction. (CLO 4, 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 4, C3)

HOUR 8

18. 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 4, C3)

(b) Calculate the theoretical yield of AgCl. (CLO 4, C3)
(c) How many grams of silver ions were present in the solution? (CLO 4, C3)

19. 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 4,C3)

(b) Determine the limiting reactant if 300 g of hematite and 60 g of CO are used in the (CLO 4, C3)
extraction.

(c) Calculate the mass of iron produced and the percentage yield if the mass of iron extracted is 70g.

(CLO 4, C3)

(d) Determine the mass of the excess reactant remained after the reaction had ceased. (CLO 4, C3)

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CHEMISTRY DK014
MATRIKULASI KPM
SISTEM EMPAT SEMESTER (S4S)

HOUR 9

20. (a) Hydrogen sulphide gas burn in air to form gaseous sulphur dioxide and steam. Write the complete
balanced chemical equations for the reaction. (CLO 4, C2)

(b) 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
i. Determine the oxidation number of the underline elements. (CLO 4, C2)

ii. Write half equations and balance the redox equation for the above reaction.

(CLO 4, C3)

iii. KMnO4 solution with concentration 0.500 M was completely oxidised the oxalate ion, determine

the volume of KMnO4 solution required for the reaction. (CLO 4, C3)

21 (a) 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) (CLO 4, C1)
i. Define limiting reactant.

ii. Determine the limiting reactant. (CLO 4, C3)

(b) 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.

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