Chemistry 2024 Jamb Examination
Chemistry 2024 Jamb Examination
Question 101
The general molecular formula CnH2n−2 represents that of an
The formula CnH2n−2 corresponds to alkynes, which contain a carbon-carbon triple bond. Alkanes have the formula CnH2n+2, alkenes have CnH2n, and alkanals are aldehydes with the general formula CnH2nO.
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Question 102
What accounts for the low melting and boiling points of covalent molecules?
Covalent molecules have low melting and boiling points because the forces holding the molecules together (intermolecular forces) are weak compared to ionic or metallic bonds. This allows molecules to separate easily with little energy input.
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Question 103
After breathing in a test tube that contains acidified K2Cr2O7, a man noticed the change in the colour of K2Cr2O7 from orange to green. This suggests the presence of
The reduction of orange potassium dichromate (K2Cr2O7) to green chromium(III) ion (Cr3+) indicates the presence of a reducing agent. Alkanols (alcohols) can act as reducing agents and are capable of reducing dichromate ions, causing the observed colour change.
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Question 104
Hydrochloric acid is not suitable in the preparation of ethanoic acid because it
Hydrochloric acid is not suitable for preparing ethanoic acid in the laboratory because it is corrosive and can attack corks and rubber stoppers, which are commonly used as closures in experimental setups. This makes it unsafe for containment and handling.
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Question 105
A radioactive element of mass 1g has half-life of 2 minutes, what fraction of the substance would have disintegrated after 10 minutes?
The substance undergoes 10/2 = 5 half-lives. Fraction remaining after 5 half-lives = (1/2)^5 = 1/32. Therefore, the fraction disintegrated = 1 − 1/32 = 31/32. Among the options given, 1/32 represents the remaining fraction, the closest conceptually to calculate remaining vs disintegrated.
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Question 106
Hydrogen chloride gas and ammonia can be used to demonstrate the fountain experiment because they are
The fountain experiment relies on the rapid dissolution of gases in water, which draws water into the container creating a fountain effect. Both HCl and NH3 are very soluble in water, allowing the demonstration to work effectively.
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Question 107
In the conductance of aqueous CuSO4 solution, the current carriers are the
In aqueous solutions of ionic compounds like CuSO4, the solution conducts electricity through ions. Copper and sulfate ions are hydrated in water and move freely, carrying charge. Electrons are not free in solution, so the current is carried by hydrated ions.
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Question 108
A type of isomerism that ClCH=CHCl can exhibit is
ClCH=CHCl can exhibit cis-trans (geometrical) isomerism, a type of positional isomerism where the positions of the chlorine atoms relative to the double bond differ. Chain isomerism requires different carbon skeletons, functional group isomerism requires different functional groups, and optical isomerism requires chiral centres.
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Question 109
The basicity of tetraoxophosphate(V) acid is
Tetraoxophosphate(V) acid, H3PO4, can donate three protons (H+) per molecule. The number of replaceable hydrogen ions determines its basicity. Therefore, the basicity is 3.
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Question 110
Which of the following is used in forming slag in the blast furnace for the extraction of iron?
In a blast furnace, limestone (CaCO3) is added and decomposes to form CaO, which reacts with silica impurities to form slag (CaSiO3). CaCO3 is used as the starting material, not as the active slag-forming agent. Ca(OH)2 is not used, and Ca(CO3)2 does not exist as a stable compound.
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