Waec 2023 Chemistry Practical Question and Answers.
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(7a)
Fiber optics refers to a technology that utilizes thin, flexible strands of glass or plastic called optical fibers to transmit information in the form of light pulses.
OR
Fiber optics refers to the technology that uses thin strands of glass or plastic fibers to transmit data and information in the form of light signals.
OR
Fiber optics is a method of transmitting light signals through optical fibers for the purpose of communication or data transmission.
(7b).
(i) Optical fibers have a much higher bandwidth compared to copper cables.
(ii) Optical fibers can transmit signals over much longer distances without experiencing significant signal degradation unlike copper cables which are limited in their transmission.
(iii) Optical fibers are immune to Electromagnetic Interference while copper cables are susceptible to interference
(iv) Optical fibers offer improved security for data transmission whereas copper cables are vulnerable to eavesdropping or unauthorized access
(v) Optical fibers are much thinner and lighter than copper cables, making them easier to install and handle.
*Diffusion refers to the process by which fluid molecules or particles move from an area of higher concentration to an area of lower concentration. This movement occurs due to the random motion of molecules, as described by the kinetic theory.
OR
Diffusion is the spontaneous movement of fluid molecules from an area of high concentration to an area of low concentration. According to the kinetic theory, molecules possess kinetic energy and random motion, leading to collisions and subsequent redistribution, resulting in the even distribution of molecules throughout the fluid.
OR
Diffusion is the process by which fluid molecules move from a higher concentration area to a lower concentration area. According to the kinetic theory, fluid molecules are in constant motion, colliding with each other and their surroundings. These collisions cause them to move randomly, leading to the gradual spreading and intermingling of molecules throughout the fluid.
(5bi).
-Interference
-Diffraction
-Doppler Effect
-Polarization
-Refraction
-Dispersion
(5bii).
-Particle-Wave Duality.
-Photoelectric Effect
-Photoionization
-Compton Scattering.
Geostationary satellites:
(i) Orbit the Earth directly above the equator in a geosynchronous orbit
(ii) It has an inclination of 0 degrees
(iii) Its coverage are limited to a specific longitude
(iv) They observe the Earth from a fixed position, providing a continuous view of a specific region
(v) They collect data for meteorological observations, weather forecasting, and telecommunications
(vi) They are positioned at an altitude of approximately 35,786 kilometers
(vii) They provide a continuous stream of data and observations for a specific region, allowing for real-time.
Polar satellites:
(i) Orbit the Earth in a polar orbit
(ii) It has a high inclination angle (usually around 90 degrees)
(iii) They cover the entire Earth's surface over time.
(iv) They observe the Earth from a changing perspective as they orbit, resulting in different views of the Earth's surface with each pass.
(v) They collect data for a wide range of applications, including weather monitoring, climate research, environmental monitoring, and scientific research.
(vi) They operate at lower altitudes, typically between 700 and 1,500 kilometers
(vii) They have a lower data refresh rate since they pass over a given area less frequently.
(1a)
Incomplete records refer to financial records that are missing some or all of the necessary information needed to prepare a complete set of financial statements.
(1b)
(i) Increases the risk of errors: When records are incomplete, there is a greater likelihood of errors being made in the data that is recorded. This can lead to inaccurate financial statements, incorrect tax filings, and ultimately, financial losses for the business.
(ii) Difficulty in making informed decisions: Incomplete records can make it challenging for the management to make informed decisions. When there is a lack of accurate can lead to inaccurate reporting and decision-making based on faulty or incomplete data.
(iii) Legal and Compliance Risks: A company with incomplete records may have trouble meeting legal obligations such as tax regulations and employment laws. Incomplete records can also make it difficult to comply with audits and investigations.
(iv) Impacts on Business Decision-Making: Incomplete records can also limit the ability of a company to make informed business decisions. Without accurate and up-to-date records, a company may miss critical information or opportunities, leading to suboptimal decision-making and ultimately, negative impacts on the business's bottom line.
(1c)
(i) Lack of knowledge: Business owners may not have enough knowledge about bookkeeping and accounting practices. This lack of knowledge may result in incomplete records or improper recording of transactions. They may not have the proper accounting software and may not hire a professional bookkeeper, which results in incomplete and inaccurate records.
(ii) Time constraints: Business owners may not have enough time to maintain complete records due to other pressing business concerns. This may mean that they only record certain transactions and disregard others.
(iii) Disorganized record-keeping: Lack of organization or a systematic record-keeping process can result in incomplete records. If businesses do not have a clear system for documenting and organizing their financial transactions, they may miss recording some transactions.
1a.
Transition elements are the elements in the central block of the periodic table, from groups 3 to 12. They are characterized by having partially filled d orbitals in their outer electron shells, which gives rise to their unique properties, such as variable oxidation states, colored compounds, and complex formation.
(c) The general increase in the first ionisation energies across a period in the periodic table is due to the increasing effective nuclear charge experienced by the outermost electrons. As the atomic number increases, the number of protons in the nucleus increases, which attracts the negatively charged electrons more strongly and increases the energy required to remove them. Additionally, the decreasing atomic radius also contributes to the increase in ionisation energy, as the outermost electrons are held more tightly by the smaller, denser nucleus.
2bi.:
1) Gas particles have negligible volume compared to the volume of the container.
2) Gas particles do not interact with each other.
2bii. Real gases do not obey these postulates because they have non-zero molecular volumes and exhibit intermolecular forces of attraction. In real gases, the volume of the gas molecules and their interactions with each other become significant at high pressures and low temperatures, causing deviations from the ideal gas law. These deviations can be accounted for using corrections such as the van der Waals equation of state.
[5/24, 12:03 PM] +234 802 342 9251: Section B.
2a. (i) The balanced equation for the reaction is:
NaOH + H2SO4 → Na2SO4 + 2H2O
(2aii) To calculate the concentration of the acid in mol dm^-3, we need to use the equation:
n = m/M
n NaOH = 4 g / 40 g mol^-1 = 0.1 mol
Since 8.0 cm³ of the acid was used to neutralize the sodium hydroxide, we can use the equation:
n acid = c × V
c = n acid / V
Substituting the values we know, we get:
c = 0.1 mol / 0.008 dm³ = 12.5 mol dm^-3
There fire the concentration of the acid in mol dm^-3 is 12.5 mol dm^-3.
2bi.
i.The postulate that gases consist of small, spherical particles in constant random motion.
ii.The postulate that gas particles have no attraction or repulsion for each other.
2bii)
The Kinetic theory of gases describes how gases behave, but it's not entirely accurate for real gases. The theory assumes that gas particles are small and move randomly, and that they don't attract or repel each other. However, real gases have more complex behavior, and their particles can be different sizes and shapes.
[5/24, 12:04 PM] +234 802 342 9251: Number 3
3a.
The empirical formula of the compound with 52.2% C, 13.1% H, and 34.7% O and a vapor density of 23 is C2H6O.
3aii
The empirical formula C2H6O has a molar mass of 2(12.01 g/mol) + 6(1.01 g/mol) + 16.00 g/mol = 46.08 g/mol.
The vapor density of the compound is 23, which is half of its molar mass. Therefore, the molar mass of the compound is 46.08 g/mol x 2 = 92.16 g/mol.
To find the molecular formula, we need to divide the molar mass of the compound by the molar mass of the empirical formula:
92.16 g/mol ÷ 46.08 g/mol = 2
The molecular formula is therefore twice the empirical formula:
C4H12O2
Therefore, the molecular formula of the compound is C4H12O2.
3aiii.
(I)the functional group present in the compound is carboxylic acid and alcohol. The compound reacts with sodium metal, indicating the presence of a carboxylic acid group.
ii. The structural formula of glucose is:
HOCH2(CHOH)3CHO
And the structural formula of fructose is:
HOCH2(CHOH)3CO.
3b.
Chemical equation for the production of ethanol from cooked cassava is (C6H10O5)n + nH2O → nC6H12O6 → 2nC2H5OH + 2nCO2.
3ci.
When aluminium is exposed to air, it forms a thin layer of aluminium oxide on its surface that protects it from reacting with water. This layer reacts with water to form a different compound that also protects the metal from further reaction with water. This is why aluminium does not react with water in a way that produces hydrogen gas.
3cii. To make pure aluminium chloride crystals, mix aluminium with hydrochloric acid, evaporate water, cool, crystallize, clean, and dry.
3d. To separate water from CuSO4, heat the aqueous solution until water evaporates, leaving solid CuSO4.
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2ci. The compound is called hexane-1,2,3,4,5,6-hexol, also known as sorbitol.
2cii.
-mannitol
-dulcitol.
2ciii. Sorbitol is made from starch by a process called hydrogenation. First, starch is broken down into glucose. Then, the glucose is treated with hydrogen gas and a metal catalyst to turn it into sorbitol. Finally, the sorbitol is purified and separated.
2civ.
C6H12O6 + H2 → C6H14O6
In this equation, glucose (C6H12O6) reacts with hydrogen gas (H2) in the presence of a metal catalyst to produce sorbitol (C6H14O6).
2cv.
Alpha-amylase
glucoamylase.
CHEMISTRY OBJECTIVES ANSWERS
01-10: ACADABBDAC
11-20: BCACBBCCBA
21-30: ACBABDCCCB
31-40: CBBDAABDAD
41-50: ACCDABDDCD.
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