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Chemistry
WAEC / WASSCE 1999
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Equal volumes of water were added to one mole of each of the following compounds. Which of them produced the largest number of ions
A
Glucose
B
Sodium trioxonitrate (V)
C
Ethananoic acid
D
Silver chloride
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #36722)
Chemistry
WAEC / WASSCE 1999
Oxidation, Reduction & Redox Reactions
When dilute copper (ll) chloride solution is electrolysed, the reaction at the cathode is represented by the equation
A
Cu → Cu2+ + 2e-
B
Cu2+ + 2e- → Cu
C
40H- - 4e- → O2 + 2H2O
D
2CI- → CI2 + 2e
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #36723)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry I: Hydrocarbons & Crude Oil
How many carbon atoms are present in one molecule of 2-methylpropane?
A
2
B
3
C
4
D
5
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #36725)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry I: Hydrocarbons & Crude Oil
Which of the following is the most reactive towards bromine?
A
Methane
B
Benzene
C
Ethyne
D
Hexane
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #36726)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry I: Hydrocarbons & Crude Oil
Which of the following compounds is unsaturated?
A
2-methylbutane
B
Chloromethane
C
Methylbenzene
D
1,2-dibromoethane
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #36727)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Alkanoates are produced from alkanols by
A
fermentation
B
saponification
C
oxidation
D
esterification
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #36729)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Which of the following is a secondary alkanol?
A
OHCI2-CH2OH
B
H2C=CH-CH2OH
C
CH 3-CH(OH)-CH 3
D
CH3-(CH2)3-CH2OH
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #36732)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry I: Hydrocarbons & Crude Oil
Geometric (cis-trans) isomerism is exhibited by
A
C 2H 2CI 2
B
CH2CI5
C
C 4H 10
D
C5H12
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #36734)
Chemistry
WAEC / WASSCE 1999
Metals, Transition Elements & Extraction
Which of the following is needed to produce slag during the extraction of iron in the blast furnace?
A
Cryolite
B
Limestone
C
Carbon
D
Sulphur
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #36735)
Chemistry
WAEC / WASSCE 1999
Air & Environmental Chemistry
Environmental pollution problems are generally more severe in countries which have
A
dense population
B
low birth rate
C
great land mass
D
limited industries
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #36736)
Chemistry
WAEC / WASSCE 1999
Air & Environmental Chemistry
The greenhouse effect is a climatic condition associated with the presence of excess
A
carbon (IV) oxide
B
hydrogen sulphide
C
nitrogen (ll) oxide
D
ammonia gas
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #36737)
Chemistry
WAEC / WASSCE 1999
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
All your burette readings (initial and final), as well as the size of your pipette, must be recorded but on no account of experimental procedure is required. All calculations must be done in your answer book.
(a) Put A into the burette and titrate it against 20.0 cm\(^3\) or 25.0 cm\(^3\) portion of B using methyl orange as indicator. Record the volume of your pipette. Tabulate your burette readings and calculate the average volume of A used. The equation for the reaction is 2NaOH\(_{(aq)}\) + H\(_2\)X\(_{(aq)}\) \(\to\) 2H\(_2\)O\(_{(l)}\)
(b) From your results and the information provided, calculate the;
(i) Concentration of solution B in mol dm\(^{-3}\)
(ii) concentration of solution A in mol dm\(^{-3}\)
(iii) molar mass of the acid H\(_2\)X. [H = 1, O = 16, Na = 23]
A
carbon (IV) oxide
B
hydrogen sulphide
C
nitrogen (ll) oxide
D
ammonia gas
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Rough
1st Reading
2nd Reading
3rd Reading
Final Burette Reading
24.0
23.60
24.15
28.55
Initial Burette Reading
0.00
0.00
0.50
5.00
Volume of A used
24.00
23.60
23.65
23.55
Indicator used - Methyl orange
Colour change at end point from yellow to pink
Volume of pipette 25 cm\(^3\)
Average titre = \(\frac{23.60 + 23.65 + 23.55}{3}\) = \(\frac{70.80}{3}\)
= 23.60 cm\(^3\)
(b)(i) Concentration of B Molar (formula) mass of NaOH = (23 + 16 + 1) or 40g mol\({-1}\)
Mass of NaOH in 1 dm\(^3\) of solution of B = \(\frac{2.15 \times 1000}{250}\)
OR 2.15 x 4 = 8.60 g dm\(^{-3}\)
Concentration of solution of B = \(\frac{8.60}{40}\) = 0.215 mol dm\(^{-3}\)
(ii) Equation for the reaction; 2 NaOH + H\(_2\)X \(\to\) Na\(_2\)X + 2H\(_2\)O
\(\frac{\text{No. of moles of A(C\(_A\)) x volume of A (V\(_A\))}}{\text{No of moles of B(\(C_B\)) x volume of B(V\(_B\))}}\) = molar ratio of \(\frac{A}{B}\)
\(\frac{C_A \times V_A}{C_B \times V_B} = \frac{1}{2}\)
\(\frac{C_A \times 23.6}{0.125 \times 25} = \frac{1}{2}\)
C\(_A\) = \(\frac{0.245 \times 25}{2 \times 23.6}\) = 0.144 mol dm\(^{-3}\) to 3 sig. fig.
(iii) Molar mass of H\(_2\)X, concentration in mol dm\(^{3}\) = \(\frac{\text{mass per dm\(^3\)}}{\text{Molar mass}}\)
Molar mass of H\(_2\)X = \(\frac{3.70}{0.114}\)
Source: Official Exam / Past Question Archive
Chemistry
WAEC / WASSCE 1999
Kinetic Theory of Matter & Gas Laws
Solution
(a)(i) State three postulates of the kinetic theory of gases.
(ii) Draw a sketch to illustrate Boyle's law.
(iii) Explain what is meant by "absolute zero of temperature".
(b) Equal volumes of a gas X and oxygen are at the same pressure but temperature of 200 K and 800K respectively.
(i) Giving reason for your answer, state which of the gas samples contains the greater number of molecules.
(ii) If the mass of one molecule of the gas X is 2.19 x 10\(^{-22}\) g, determine the molar mass of X. [Avogadro constant = 6.02 x 10\(^{-23}\)]
(iii) Hence, state with reason which of X and oxygen will diffuse faster under the same conditions. [O= 16].
(c)(i) Mention two reaction conditions that can increase the yield of ammonia in the reaction represented by the following equation: N\(_{2(g)}\) + 3H\(_{2(9)}\) \(\rightleftharpoons\) 2NH\(_{3(g)}\) \(\Dellta\)H = -46kJmol\(^{-1}\). Draw a labelled energy profile diagram for an endothermic reaction.
(iii) A solid W decomposes on heating according to the following equation: W\(_{(s)} \to Y_{(s}) + Z_{(g)}\) List two factors apart from temperature, which can affect the rate of the reaction.
medium Difficulty
Verified Correct Answer: Option
Chemical Principles & Mechanism
(a)(i) Postulates of the kinetic theory of gases: Gas molecules move randomly in straight lines. They collide with one another and with the walls of the container. The temperature of the gas is a measure of the average kinetic energy of the molecule. The forces of attraction between gas molecules are negligible. The volume occupied by gas molecules is negligible compared to the volume of the container. The collision of the molecules is perfectly elastic (any three).
(ii) Sketches to illustrate Boyle's Law
(iii) Absolute zero of temperature is the temperature at which the volume of a gas would be (theoretically) reduced to zero. OR It is the temperature at which all motion is assumed to have ceased. OR It is the lowest temperature theoretically possible OR It is temperature at which all gases liquefy or solidify OR the entropy of the system is at rest.
(b) If equal volumes of gas X and oxygen are at the same pressure but at 200 K and 800 K respectively:
(i) X contains the greater number of molecules; Reason: Since X is at a lower temperature, it must contain more molecules to be able to exert the same pressure Alternatively n = \(\frac{PV}{RT}\)
n\(_x\) = \(\frac{PV}{200R}\)
nO\(_2\) = \(\frac{PV}{800R}\)
Hence, n\(_x\) is greater
(ii) To calculate molar mass of X if one molecule of it has a mass of 2.19 x 10\(^{-22}\)g. Calculation: 1 mole of x contains 6.02 x 10\(^{23}\) molecule.
1 mole of x will have a mass of (2.19 x 10\(^{-22}\) x 6.02 x 10\(^{23}\))g = 131.84 g mo1\(^{-1}\) ; approximately 132g mol\(^{-1}\).
(iii) Comparison of rate of diffusion of X with that of oxygen: O\(_2\) will diffuse faster. The lighter the gas, the faster the rate of diffusion. The molar mass of O\(_2\) is 32g. Hence it is lighter than X and will diffuse faster.
(c)(i) Increasing the pressure or increasing the concentration of reactions of the left hand side.
-lowering the temperature of the system.
-Continuous removal of NH\(_3\) as it is produced. (any two)
(ii) Energy profile diagram for an endothermic reaction.
(iii) in the reaction represented by the following equation W_(s)\) —> Energy Yv + Z\(_(s)\). Reaction rate can be affected by the following factors apart from temperature.
- Surface area / particle size
- Presence of catalyst.
Source: Myschool Past Questions Archive (Record #54197)
Chemistry
WAEC / WASSCE 1999
Atomic Structure, Orbitals & Nuclear Chemistry
Solution
a)(i) State three differences between covalent compounds and electrovalent compounds.
(ii) Two elements represented as K and L have atomic numbers of 12 and 8 respectively. Write their electronic structures and state the group to which each belongs in the Periodic Table.
(iii) If an alkali metal M exists naturally as the oxide, state with reason whether or not M can be extracted by reduction of the oxide with coke.
(b)(i) What is meant by the half-life of a radioactive element?
(ii) Mention the radioactive isotope used in dating archaeological specimens.
(iii) Balance the following equation and identify Q,
\(^{28}_{13}Al\) —> \(^{24}_{13}Si + \(^{0_1Q\)
(c)(i). Give three chemical properties of metals.
(ii) State two reasons why duralumin preferred to steel in aircraft manufacture.
(iii) What term is used to describe the ability of metals to be hammered into thin sheets?
(iv) Calculate the number of mole of electrons involved in the oxidation of 2.8g of iron filings to iron (II) ions. [Fe = 56].
medium Difficulty
Verified Correct Answer: Option
Chemical Principles & Mechanism
(a)(i) - Covalent compounds contain only molecules while electrovalent compounds do not contain molecules
- Covalent compounds usually dissolve in covalent organic Products compounds but not in water but electrovalent compounds are soluble in water
- Covalent compounds are usually volatile with low melting and boiling points but electrovalent compounds usually have high melting and boiling points.
(ii) \(_{12}\)K has an electronic structure of 1s\(^2\)2\(^2\)2p\(^6\)3s\(^2\); L has the structure of 1s\(^2\)2s\(^2\)2p\(^4\); belongs to group II and L to group VI
(iii) Alkali metal M cannot be extracted by reduction of the oxide with oxide coke because of its high stability and reactivity.
(b)(i) The half-life of a radioactive element is the time it takes for one half of any quantity of a radioactive molecule to decay. It is therefore also equal to the time for the amount of the radioactive nuclide present to fall from one half to one quarter, from one quarter to one eight, etc.
(ii) The radioactive isotope normally used in dating archaelogical specimens is carbon - 14.
(iii) \(^{28}_{13}Al\) -> \(^{28}_{14} Si\) + \(^0_{-1}Q\)
(c)(i) - electropositive
- form electrovalent chlorides
- Replace the hydrogen in acid if more electropositive than hydrogen
-Form metallic hydrides/ionic hydrides.
(ii) Duralumin is preferred to steel in aircraft manufacture because duralumin is lighter and more resistant to corrosion.
(iii) The ability of metals to be hammered into thin sheet is described as malleability.
(iv) To calculate the number of mole of electrons involved in the oxidation of 2.8g of iron filing to Fe\(^{2+}\) + Fe —> Fe\(^{2+}\) + 2e\(^{-}\) ; 56g of Fe loses 2 mole of electrons.
2.8 of Fe would lose \(\frac{2.8 \times 2}{56}\) = 0.10 mole
Source: Myschool Past Questions Archive (Record #54198)
Chemistry
WAEC / WASSCE 1999
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
(a) The letters R,S,T represent an alkene, an alkene and a terminal alkyne respectively. Which of R, S and T typically undergo(es) the following reactions?
(i) Addition reaction;
(ii) Combustion;
(iii) Substitution reaction.
(b)(i) Name the process by which an alkanol can be converted to an alkene.
(ii) Write the name and structural formula of the third member cf the alkanol series.
(iii) State what would be obtained if a primary alkanol reacted with excess acidified KMnO\(_4\) solution.
(c)(i) Give one chemical test for alkanoic acids.
(ii) Write an equation to show how methanoic acid reacts with ethanol in the presence of mineral acids.
(iii) What is the role of mineral acid in the reaction in (c) ii?
(d) In an experiment, cassava was pressure-cooked to release starch granules, followed by treatment with malt for about 2 hours at 55^\circC. Yeast was then added and the mixture was left for 2 days at 27^\circC. An organic product J and a gas H were obtained.
(i) Identify H
(ii) State the class of carbohydrates to which starch belongs and explain what happened to the starch during treatment with malt.
(iii) Draw a labelled diagram of a suitable set-up for obtaining a sample of J from the reaction mixture.
medium Difficulty
Verified Correct Answer: Option
Chemical Principles & Mechanism
(a) If R, S and T respectively are an alkene, alkene and a terminal alkyne:
(i) S and T would undergo addition reaction.
(ii) k, S and T would undergo combustion.
(iii) R and T would undergo substitution.
(b)(i) An alkanol is converted into an alkene by dehydration.
(ii) The third member of the alkanol series is propanol or propan - 2 - ol.
(iii) A primary alkanol reacts with excess acit'ified
(c)(i) Chemical test for alkanoic acid: Add (saturated) NaHCO\(^{3}\) or Na\(_2\)CO\(_3\)(solution), effervescence or gas evolved indicating alkanoic acid.
(ii) The reaction of methanoic acid with ethanol in the presence of mineral acid.
Equation: HCOOH + CH\(_3\)CH\(_2\)OH —> HCOOC\(_2\)H\(_5\) + H\(_2\)O
(iii) Role of mineral acid in (ii) above, is catalysis or acts as catalyst
(d) Cassava was pressure-cooked, then malt was added at 55^\circC for 2 hours followed by yeast. After 2 days at 27`C an organic product J and gas H were obtained
(i) H was CO\(_2\).
(ii) Starch is polysaccharide / complex carbohydrate. During treatment with malt, it was hydrolysed by diastascgcmylase Diastase
in malt to sugar / maltose.
(C\(_6\)H\(_{10}\)O\(_5\))n + nH\(_2\)O \(_n\)C\(_12\)H\(_{22}\)O\(_{11}\)
Source: Myschool Past Questions Archive (Record #54199)