Chemistry 2018 Jamb Examination
Chemistry 2018 Jamb Examination
Question 41
When air which contains the gases oxygen, nitrogen, carbon dioxide, water vapour and the rare gases is passed through alkaline pyrogallol and then over quicklime, the only gases left are:
Alkaline pyrogallol absorbs oxygen gas, while quicklime (CaO) removes carbon dioxide by forming calcium carbonate. The remaining gases—nitrogen and the rare (noble) gases—do not react with either reagent and therefore remain in the mixture.
Hence, after the absorption process, only nitrogen and the rare gases are left.
Hence, after the absorption process, only nitrogen and the rare gases are left.
Not clear enough?
Question 42
In the laboratory preparation of oxygen, the gas cannot be collected by downward displacement of air because
Oxygen has almost the same density as air, making separation by displacement inefficient. Since the two gases mix readily, collecting oxygen by downward displacement of air is impractical. Therefore, it is collected over water or by upward delivery instead.
Not clear enough?
Question 43
2KClO₃(s) → 2KCl(s) + 3O₂(g)
The importance of the catalyst in the reaction above is that
The importance of the catalyst in the reaction above is that
Potassium chlorate decomposes to give oxygen gas when heated, and manganese(IV) oxide is commonly used as a catalyst. The catalyst lowers the activation energy and allows the reaction to proceed faster at a lower temperature without affecting the amount of oxygen produced.
Not clear enough?
Question 44
Which of the following is used to power steam engines?
Steam engines are traditionally powered by the combustion of coal. The heat generated from burning coal is used to convert water into steam, which drives the engine pistons or turbines to produce mechanical work.
Hence, coal is the fuel used to power steam engines.
Hence, coal is the fuel used to power steam engines.
Not clear enough?
Question 45
In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10 cm³ of 1.25 molar sulphuric acid?
The reaction is 2NaOH + H2SO4 → Na2SO4 + 2H2O .
\( C_1V_1/n_1 = C_2V_2/n_2 \)
For NaOH: \( C_1 = 0.5, n_1 = 2 \)
For H₂SO₄: \( C_2 = 1.25, V_2 = 10, n_2 = 1 \)\[ V_1 = \dfrac{C_2V_2n_1}{C_1n_2}\]\[ = \dfrac{1.25 \times 10 \times 2}{0.5 \times 1} = 50 \; \text{cm}^3 \]Thus, 50 cm³ of 0.5 M NaOH will exactly neutralise 10 cm³ of 1.25 M H₂SO₄.
\( C_1V_1/n_1 = C_2V_2/n_2 \)
For NaOH: \( C_1 = 0.5, n_1 = 2 \)
For H₂SO₄: \( C_2 = 1.25, V_2 = 10, n_2 = 1 \)\[ V_1 = \dfrac{C_2V_2n_1}{C_1n_2}\]\[ = \dfrac{1.25 \times 10 \times 2}{0.5 \times 1} = 50 \; \text{cm}^3 \]Thus, 50 cm³ of 0.5 M NaOH will exactly neutralise 10 cm³ of 1.25 M H₂SO₄.
Not clear enough?
Question 46
To what volume must 300 cm³ of 0.60 M sodium hydroxide solution be diluted to give a 0.40 M solution?
Using the dilution formula \( C_1V_1 = C_2V_2 \):
\( 0.60 \times 300 = 0.40 \times V_2 \)
\( V_2 = \dfrac{0.60 \times 300}{0.40} = 450 \; \text{cm}^3 \)
Therefore, the solution must be diluted to 450 cm³ to achieve a 0.40 M concentration.
\( 0.60 \times 300 = 0.40 \times V_2 \)
\( V_2 = \dfrac{0.60 \times 300}{0.40} = 450 \; \text{cm}^3 \)
Therefore, the solution must be diluted to 450 cm³ to achieve a 0.40 M concentration.
Not clear enough?
Question 47
Diamond is a bad conductor of electricity because its bonding electrons are used in
Each carbon atom in diamond forms four strong covalent bonds in a tetrahedral arrangement, using all its valence electrons. This leaves no free electrons or mobile charge carriers for conduction, making diamond an electrical insulator.
Not clear enough?
Question 48
The reaction between an organic acid and an alcohol in the presence of an acid catalyst is known as:
An organic acid reacts with an alcohol in the presence of an acid catalyst (usually concentrated Hâ‚‚SOâ‚„) to form an ester and water. This process is known as esterification.
Example: \( CH_3COOH + C_2H_5OH \xrightarrow{H_2SO_4} CH_3COOC_2H_5 + H_2O \)
Example: \( CH_3COOH + C_2H_5OH \xrightarrow{H_2SO_4} CH_3COOC_2H_5 + H_2O \)
Not clear enough?
Question 49
The constituent common to duralumin and alnico is
Both duralumin and alnico contain aluminium (Al).
Duralumin is an alloy of aluminium, copper, magnesium, and manganese, while alnico is made of aluminium, nickel, and cobalt. Therefore, aluminium is the common constituent between the two alloys.
Duralumin is an alloy of aluminium, copper, magnesium, and manganese, while alnico is made of aluminium, nickel, and cobalt. Therefore, aluminium is the common constituent between the two alloys.
Not clear enough?
Question 50
The solubility of solids that dissolve in a given solvent with the liberation of heat will
When dissolution is exothermic (heat is released), increasing the temperature shifts the equilibrium to favour the undissolved solid, reducing solubility.
Therefore, solubility decreases with an increase in temperature for such substances.
Therefore, solubility decreases with an increase in temperature for such substances.
Not clear enough?
You might like
When the correct SQL command is used to delete a table's structure, what happens to the data in the table?
Select the option that is related to the third number in the same way as the second number is related to the first number. 9 : 21 :: 27 : _ ?
Three boys shared some oranges. The first received 1/3 of the oranges and the second received 2/3 of the remainder. If the third boy received the remaining 12 oranges,how many oranges did they share?
Which of the following keyboard combinations is used to 'cut' highlighted text in the Windows operating system?