JAMB Chemistry 2023
The separation scheme for a mixture of common salt, sand and ammonium chloride is
Correct Answer: B) sublimation, addition of water, filtration
Which of the following substances is not a strong electrolyte?
Correct Answer: C) H₂O
A mixture of calcium chloride and calcium trioxocarbonate(IV) is heated. The gas evolved will turn moist blue litmus paper to
Correct Answer: C) red
In the preparation of a standard solution of H₂SO₄, the acid is usually diluted by adding
Correct Answer: B) water to acid
Which of the following pairs of substances will react further to produce a precipitate when NaOH solution is added to a mixture of the salts?
Correct Answer: B) FeSO₄(aq) and (NH₄)₂SO₄(aq)
The gas that is most useful for the protection of the environment is
Correct Answer: C) N₂
Which of the following will precipitate when silver nitrate solution is added to a solution containing the ions Ca²⁺, Zn²⁺, Na⁺, and Cl⁻?
Correct Answer: D) Cl⁻ only
In the preparation of some pure gases, drying agents are often used. Which of the following drying agents is suitable for drying ammonia gas?
Correct Answer: C) CaO
The reaction of halogens in order of decreasing reactivity with aqueous sodium hydroxide is
Correct Answer: C) Cl₂ > I₂ > Br₂
A mixture of sugar and sulphur can be separated by
Correct Answer: B) dissolution in water, filtration and sublimation
Which of the following salts will undergo hydrolysis?
Correct Answer: C) NH₄Cl
A mixture of sand and iodine can be separated by
Correct Answer: D) decantation
Consider the reaction represented by: xPb(NO₃)₂ → 2PbO + yNO₂ + zO₂. What are the values of x, y and z respectively?
Correct Answer: C) 2, 4, 1
20 cm³ of H₂ mixed with 100 cm³ of air containing 21% O₂. Calculate the volume of the residual gases at 110 °C.
Correct Answer: D) 110 cm³
What is responsible for metallic bonding?
Correct Answer: B) Attraction between the atomic nuclei and the cloud of electrons
25 cm³ of 1.5 M solution of NaCl are added to 50 cm³ of 3 M NaCl. The molar concentration of the resulting solution is
Correct Answer: A) 2.5 M
A solution of salt formed from HCl and NH₃ solutions is
Correct Answer: A) acidic
Which of the following elements will burn in excess oxygen to form a product that is neutral to litmus?
Correct Answer: B) Hydrogen
A current was passed for 10 mins and 0.2 mole of Cu was deposited. How many grammes of Ag will it deposit? (Cu = 64, Ag = 108)
Correct Answer: A) 43.2g
Pollution of underground water by metal ions is very likely in a soil that has high
Correct Answer: D) nitrate content
The presence of NaCl in ice will
Correct Answer: D) lower the melting point of ice
What are the values of x, y and z in the equation below? xNH₃ + yO₂ → zNO + 6H₂O
Correct Answer: B) 4, 5, 4
Calculate the volume of CO₂ measured at s.t.p produced on heating 250g of potassium hydrogen trioxocarbonate(IV) strongly. (K = 39, H = 1, C = 12, O = 16)
Correct Answer: A) 28 dm³
The boiling points of water, ethanol, methylbenzene and butan-2-ol are 373.0K, 351.3K, 383.6K and 372.5K respectively. Which liquid has the highest vapour pressure at 323.0K?
Correct Answer: C) Ethanol
The conclusion from Rutherford’s alpha-scattering experiment is that
Correct Answer: A) Atoms are mostly empty space with a small nucleus
Elements P, Q and R have atomic numbers 9, 16 and 20 respectively. Which of them would gain electron(s) during ionic bonding?
Correct Answer: C) P and Q
Which of the following has the lowest pH?
Correct Answer: D) 15cm³ of M/2 HCl
Which of the following is an acid salt?
Correct Answer: C) KHSO₄
Cr₂O₇²⁻ + 14H⁺ + 6I⁻ → 2Cr³⁺ + 3I₂ + 7H₂O. The change in the oxidation number of oxygen in the equation above is
Correct Answer: A) 0
During the electrolysis of CuSO₄ solution using Platinum electrodes, which of the following occurs?
Correct Answer: D) pH of solution decreases
Crystallization is a better method of separation than precipitation because
Correct Answer: A) precipitation tends to bring other solutes out of solution
Which of the following is not a chemical change?
Correct Answer: D) dissolving powdered sulfur in carbon disulfide
An important ore of iron contains 72.36% iron and 27.64% oxygen. Determine its empirical formula
Correct Answer: A) FeO
Which of the following decreases when a given mass of gas is compressed to half its initial volume?
Correct Answer: A) average intermolecular distance
The densities of two gases X and Y are 2.5gdm⁻³ and 10.0gdm⁻³ respectively. What is the rate of diffusion of X relative to Y?
Correct Answer: D) 2:1
The properties of elements are periodic functions of their
Correct Answer: A) atomic number
Which of the following solutions containing only hydroxyl ions will liberate hydrogen gas when reacted with Mg metals?
Correct Answer: B) 1.0×10⁻¹³moldm⁻³
In the redox reaction: 2Fe²⁺ + Cl₂ → 2Fe³⁺ + 2Cl⁻
Correct Answer: B) Cl₂ is reduced because its oxidation number has decreased
During electrolysis of molten sodium chloride,
Correct Answer: C) chloride ion is oxidized
Coffee stains are removed with
Correct Answer: C) borax in water