Chemistry 2016 Jamb Examination
Chemistry 2016 Jamb Examination
Question 21
Which of the following compounds is used as a gaseous fuel?
The correct option is B. CH\(_3\)-C ≡ CH.
This compound is propyne, an alkyne used as a gaseous fuel similar to acetylene. It burns readily in air to produce heat energy. The other compounds are liquids or solids under normal conditions.
This compound is propyne, an alkyne used as a gaseous fuel similar to acetylene. It burns readily in air to produce heat energy. The other compounds are liquids or solids under normal conditions.
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Question 22
The products formed when primary alkanols are oxidized using acidified potassium tetraoxomanganate (VII) are what?
The correct option is A. CH\(_3\)CH\(_2\)CHO and H\(_2\)O.
When a primary alkanol (e.g., ethanol) is oxidized with acidified potassium tetraoxomanganate (VII), it first forms an aldehyde (ethanal) and water:
CH3CH2OH + [O] → CH3CHO + H2O
Further oxidation produces a carboxylic acid, but the question refers to the primary oxidation products.
When a primary alkanol (e.g., ethanol) is oxidized with acidified potassium tetraoxomanganate (VII), it first forms an aldehyde (ethanal) and water:
CH3CH2OH + [O] → CH3CHO + H2O
Further oxidation produces a carboxylic acid, but the question refers to the primary oxidation products.
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Question 23
Alkanols have the general molecular formula
The correct option is D. C\(_n\)H\(_{2n+1}\)OH.
Alkanols are alcohols derived from alkanes by replacing one hydrogen atom with a hydroxyl (–OH) group. Thus, their general formula is \( \text{C}_n\text{H}_{2n+1}\text{OH} \).
Alkanols are alcohols derived from alkanes by replacing one hydrogen atom with a hydroxyl (–OH) group. Thus, their general formula is \( \text{C}_n\text{H}_{2n+1}\text{OH} \).
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Question 24
Which of the following is not an alkali?
The correct option is D. Al(OH)\(_3\).
Al(OH)\(_3\) is amphoteric, meaning it can react as both an acid and a base. Alkalis are bases that dissolve in water to produce hydroxide ions, such as NaOH and Ca(OH)\(_2\). Ammonia is a weak alkali.
Al(OH)\(_3\) is amphoteric, meaning it can react as both an acid and a base. Alkalis are bases that dissolve in water to produce hydroxide ions, such as NaOH and Ca(OH)\(_2\). Ammonia is a weak alkali.
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Question 25
Which of the following statements is correct about the periodic table?
The correct option is D. The valence electrons of the elements increase progressively across the period.
Across a period, the number of valence electrons increases by one from left to right, while all elements in the same period have the same number of electron shells.
Across a period, the number of valence electrons increases by one from left to right, while all elements in the same period have the same number of electron shells.
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Question 26
The metal whose ore can be concentrated by passing it through a magnetic separator is
The correct option is A. Zn.
Zinc ore (zinc blende, ZnS) often contains magnetic impurities such as iron pyrites (FeS\(_2\)), which can be separated using a magnetic separator based on magnetic properties.
Zinc ore (zinc blende, ZnS) often contains magnetic impurities such as iron pyrites (FeS\(_2\)), which can be separated using a magnetic separator based on magnetic properties.
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Question 27
An example of an acidic oxide is
The correct option is C. SO\(_2\).
Sulphur(IV) oxide (SO\(_2\)) is an acidic oxide because it dissolves in water to form sulphurous acid (H\(_2\)SO\(_3\)) and reacts with bases to form salts.
Sulphur(IV) oxide (SO\(_2\)) is an acidic oxide because it dissolves in water to form sulphurous acid (H\(_2\)SO\(_3\)) and reacts with bases to form salts.
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Question 28
What volume of 0.5M H\(_2\)SO\(_4\) will exactly neutralize 20cm\(^3\) of 0.1M NaOH solution?
The correct option is A. 2.0cm\(^3\).
Reaction:
H2SO4 + 2NaOH → Na2SO4 + 2H2O
From the equation, 1 mole of H\(_2\)SO\(_4\) neutralizes 2 moles of NaOH.\[ M_1V_1/n_1 = M_2V_2/n_2 \]\[ 0.5V_1/1 = 0.1 \times 20 / 2 \]\[ V_1 = 2.0 \; \text{cm}^3 \] Therefore, 2.0 cm\(^3\) of 0.5M H\(_2\)SO\(_4\) is required.
Reaction:
H2SO4 + 2NaOH → Na2SO4 + 2H2O
From the equation, 1 mole of H\(_2\)SO\(_4\) neutralizes 2 moles of NaOH.\[ M_1V_1/n_1 = M_2V_2/n_2 \]\[ 0.5V_1/1 = 0.1 \times 20 / 2 \]\[ V_1 = 2.0 \; \text{cm}^3 \] Therefore, 2.0 cm\(^3\) of 0.5M H\(_2\)SO\(_4\) is required.
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Question 29
Diamond cannot be used
The correct option is A. In making bicycle chains.
Diamond is a very hard and brittle substance, making it suitable for cutting, grinding, and drilling, but not for making flexible or mechanical components like bicycle chains.
Diamond is a very hard and brittle substance, making it suitable for cutting, grinding, and drilling, but not for making flexible or mechanical components like bicycle chains.
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Question 30
Ethanol is soluble in water due to the presence of a
The correct option is B. Hydroxyl group.
The hydroxyl (–OH) group in ethanol forms hydrogen bonds with water molecules, making ethanol miscible with water in all proportions.
The hydroxyl (–OH) group in ethanol forms hydrogen bonds with water molecules, making ethanol miscible with water in all proportions.
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