# Jamb 2023 Chemistry Likely Questions & Answers Extracted From Last Year Exams

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Which of these is a derived unit?

• A. Kilogram
• B. Metre
• C. Newton
• D. Second

Explanation

Examples of Fundamental Quantities ; Mass, kilogram, kg ; Electric Current, ampere, A ; Temperature, kelvin, K ; Amount of Substance, mole, Mol.

A bar magnet is divided into two pieces, which of the following statement is correct?

• A. two new magnets are created
• B. the magnetic field of each separate piece becomes stronger
• C. the electric field is created
• D. the bar magnet is demagnetized

Explanation

When it is cut into two, the two cut pieces will have their own north and south poles since .

Consider the wave equation y = 5mm sin [1cm−1−1x – 60s−1−1t]. The wave number is?

• A. 0.1 cm−1−1
• B. 10cm−1−1
• C. 1.0cm−1−1
• D. 2cm−1−1

Explanation

The angular wave number k = 2πλ2πλ expresses the number of radians in a unit of distance.

An object 40 cm high is 30cm from the pin hole camera. If the height of the image formed is 20 cm. What is the distance of the image from the pin height?

• A. 15 cm
• B. 70 cm
• C. 40 cm
• D. 40 cm

Explanation

M → HiHoHiHo = DiDoDiDo

where M is the magnification, Hi is the height of the image, Ho is the height of the object, Di is the distance from the lens to the in-focus projected image, and Do is the distance from the object to the lens.

But Di = Hi∗DoHoHi∗DoHo → 20∗304020∗3040

Image distance(Di) = 15cm

A bar magnet is placed near and lying along the axis of a solenoid connected to a galvanometer. The pointer of the galvanometer shows no deflection when?

• A. the magnet is moved towards the stationary solenoid
• B. there is no relative motion
• C. the magnet is moved away from the stationary solenoid
• D. the solenoid is moved away from the stationary magnet

Explanation

If both the coil and the magnet are stationary, then there is no change in the magnetic flux and hence no current is induced in the coil.

• A. increase weight of tyres
• B. increase friction
• C. increase its longetivity
• D. look good

Explanation

Helps your vehicle to be able to accelerate smoothly and as well to be able to brake more quickly.

A car starts from rest and covers a distance of 40 m in 10 s. Calculated the magnitude of its acceleration

• A. 3.20 ms$$^{-2}$$
• B. 0.25 ms$$^{-2}$$
• C. 0.80 ms$$^{-2}$$
• D. 4.00 ms$$^{-2}$$

Explanation

S = ut + $$\frac{1}{2}$$at$$^2$$

40 = 0 x 10 + $$\frac{1}{2}$$a x 10$$^2$$

50a = 40

a = $$\frac{40}{50}$$

= 0.8m/s$$^2$$

The relationship between the coefficient of linear expansion αα and volumetric expansion (γγ) is—————–

• A. γγ = α−3α−3
• B. γγ = αα
• C. 3αα
• D. γγ = α3α3

Explanation

volumetric expansion (γ) = 3x Linear expansion

Which of the following is not a consequence of hydrogen bubbles covering the copper plate of a primary cell?

• A. formation of hydrogen bubbles electrode
• B. increase in the resistance of the cell
• C. local action
• D. polarization

Explanation

If the zinc used in the simple cell is of the impure commercial variety bubbles of hydrogen will be seen coming off the zinc. This is called local action.

A cell whose internal resistance is 0.55ΩΩ delivers a current of 4 A to an external resistor. The lost voltage of the cell is?

• A. 4.00 V
• B. 2.20 V
• C. 0.15 V
• D. 8.00 V

Explanation

Lost voltage = I x R

= 4 x 0.55

= 2.2V

Which of the following liquid is a poor conductor of electricity?

• A. molten mercury
• B. molten steel
• C. molten iron
• D. molten copper

Explanation

Mercury is a heavy, silvery-white liquid metal. Compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.

An isotope has an initial activity of 120 Bq. 6 days later its activity is 15 Bq. The half-life is?

• A. 3 days
• B. 2 days
• C. 1 day
• D. 4 days

Explanation

The equation that establishes a relationship between the amount left undecayed,

A, the initial amount, A0, and the number of half-lives that pass in a period of time t looks like this:

12n∗A0=A12n∗A0=A

12n∗120=1512n∗120=15

12n12n = 1512015120

12n12n = 1818

12n12n = 123123

2n=232n=23

n = 3

The secondary pigments consist of?

• A. blue, green, and violet
• B. yellow, green, and magenta
• C. magenta, yellow, and cyan
• D. red, green, and blue

Explanation

The primary colors of pigment are red, blue, and green.

Mixing these primary colors of pigment gives us the three secondary colors:

red+blue=magenta, red+ green = yellow, and blue + green = cyan

A person standing waist-deep in a swimming pool appears to have short legs because of light?

• A. diffraction
• B. refraction
• C. reflection
• D. interference

Explanation

The refractive index of water is greater than that of air.

So, A person legs appear to be short while standing in the tank due to refraction.

A tuning fork having a frequency of 312 Hz emits a wave which has a wavelength of 1.10 m. Calculate the velocity of sound

• A. 312.0 ms−1−1
• B. 110.0 ms−1−1
• C. 343.2 ms−1−1
• D. 686.4 ms−1−1

Explanation

v = f λ to calculate the wave’s velocity.

v = 312 x 1.10

= 343.2m/s

When the plate area of a capacitor increases?

• A. the voltage can withstand increase
• B. the capacitance decreases
• C. the capacitance is unaffected
• D. the capacitance increases

Explanation

Therefore, as the area of the plates increase, capacitance increases.

A magnet relay is a device used for?

• A. reading the magnitude of magnetic flux
• B. controlling another circuit carrying larger current
• C. turning in sports
• D. storing magnetic field

Explanation

Relays are electrically operated switches that open and close the circuits by receiving electrical signals from outside sources.

According to kinetic molecular model in gases,

• A. the particles are closely packed together; they occupy minimum space are usually arranged in a regular pattern
• B. the particles vibrate about fixed positions and are held together by the strong intermolecular bonds between them
• C. the molecules are very far apart and occupy all the spaces made available to them
• D. the particles occur in clusters with molecules slightly further apart

Explanation

The model, called the kinetic theory of gases, assumes that the molecules are very small relative to the distance between molecules.

The molecules are in constant, random motion and frequently collide with each other and with the walls of any container.

A current of 0.5 A flows through a resistor when connected to a 40 V battery. How much energy is dispatched in 2 minutes?

• A. 2400 J
• B. 9600 J
• C. 1500 J
• D. 1200 J

Explanation

Energy = power x time

Power = voltage x current.

Energy = voltage x current x time

Energy = 40 x 0.5 x 60 x 2

→ 2,400j

For a pear-shaped conductor shown above, the concentration of charge on the outside is highest at?

• A. X
• B. Z
• C. Y
• D. K

Explanation

The electric field at the surface of the conductor is perpendicular to the surface.

Charge accumulates, and the field is strongest, on pointy parts of the conductor.

The vapour pressure?

• A. increases non-linearly with measuring temperature
• B. increases linearly with increasing temperature
• C. decreases linearly with increasing temperature
• D. decreases non-linearly ith measuring temperature

Explanation

As the temperature of a liquid or solid increases its vapor pressure also increases.

Conversely, vapor pressure decreases as the temperature decreases.

i.e. vapor pressure is directly proportional to temperature

The potential energy in an elastic string of force constant k, which has an extension X is?

• A. kX
• B. KX22
• C. ½KX22
• D. ½K

Explanation

elastic potential energy[Ee] = 12ke212ke2.

A reservoir is filled with liquid of density 2000 kgm−1−1. Calculate the depth at which the pressure in the liquid will be equal to 9100 Nm−2−2 (g = 10 ms−2−2)

• A. 0.262 m
• B. 0.664 m
• C. 0.819 m
• D. 0.455 m

Explanation

pressure = p, depth = d, height = h, gravity = g

p = hdg

phg=dphg=d

910010∗2000=d910010∗2000=d

0.455m

Water is not a good thermometric liquid because it?

• A. expands unevenly between 0 ºC and 4 ºC
• B. maintains fixed density
• C. has high freezing point
• D. wets glass

Explanation

Water is most anomalous at low temperatures, with the remarkable density maximum at 4°C.

water is not used as thermometric liquid because it has low thermal expansivity,high specificc capacity and high vapour pressure.

Which of these is not a second class lever?

• A. sugar tongs
• B. claw hammer
• C. plier
• D. wheelbarrow

Explanation

Examples of first class levers are pliers, scissors, a crow bar, a claw hammer, a see-saw and a weighing balance.

A wheelbarrow, a bottle opener, and an oar are examples of second class levers

In the formation of sea breeze, wind blows from?

• A. sky to land
• B. sea to sky
• C. land to sea
• D. sea to land

Explanation

A sea breeze describes a wind that blows from the ocean inland towards land.

This breeze occurs most often in the spring and summer months because of the greater temperature differences between the ocean and nearby land, particularly in the afternoon when the land is at maximum heating from the sun.

Which component of fiber-optic connector has a provision of entry for the fibre along with the fixation to connector housing?

• A. coupling device
• B. cable
• C. ferrule
• D. connector housing

Explanation

Fiber optic couplers are used to split the input signals into two or more outputs, they are called splitters in this case.

On the other hand, some types of couplers can be used to combine two or more inputs into one single output, they are called combiners in this case.

In order to view the sun, the most suitable instrument to use is?

• A. helioscope
• B. telescope
• C. stroboscope
• D. sun meter

Explanation

A helioscope is an instrument used for observing the sun and sunspots.

The helioscope was first used by Benedetto Castelli and refined by Galileo Galilei.

The eclipse of the moon occurs when?

• A. the moon reflects the rays from the sun to the earth
• B. the moon comes exactly between the earth and the sun
• C. the earth comes exactly between the moon and the sun
• D. the sun comes exactly between the earth and the moon

Explanation

The moon has no light and so depends on the sun.

The same goes for the earth, when the moon comes in between the sun and earth, it block the light coming from the sun directly to earth, hence lunar eclipse occur.

The gravitational pull on the moon is 1616 that of the earth. If a body weighs 6.0 N on the moon, what will be the weight on the earth?

• A. 6.0 N
• B. 5.0 N
• C. 12.0 N
• D. 36.0 N

Explanation

A person would weigh six times less on the moon than they do on Earth.

OR

A person would weigh six times more on the earth than they do on moon.

16ofx16ofx = 6.0N on the moon

x = 6 * 6 = 36

The amount of energy required to change a kilogram of ice block into water without a change in temperature is?

• A. specific latent heat of fusion of ice
• B. specific heat capacity of rice
• C. heat capacity of rice
• D. specific heat of vaporization of rice

Explanation

Specific latent heat of fusion of a substance is the quantity of heat required to convert the unit mass of the substance from the solid to the liquid state without change in temperature.

Which expression gives magnetic flux?

• A. qVB sinθθ
• B. μϕI2πrμϕI2πr
• C. BA cos θθ
• D. -N dϕdtdϕdt

Explanation

the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface.

It is usually denoted Φ or ΦB. The SI unit of magnetic flux is the weber

Mathematically it is represented as B = Φ/A

where B is magnetic flux density in teslas (T),

Φ is magnetic flux in webers (Wb), and

A is area in square meters (m2).

The graph of pressure (P) against the reciprocal of the volume (I/V) in Boyles’s law is a?

• A. hyperbola
• B. parabola
• C. curve
• D. straight line

Explanation

The pressure (p) of a given quantity of gas varies inversely with its volume (v) at constant temperature; i.e., in equation form, pv = k, a constant.

The graph of Boyle’s law is called the PV curve.

This graph of Boyle’s law is not straight but hyperbolic; this is because the statement says that at a constant temperature the pressure and the volume are inversely proportional..

What quantity of heat is required to convert 20 g of ice at 0 ºC to water at the same temperature? (Specific latent heat of ice = 336 Jg−1−1)

• A. 7.06 x 1033J
• B. 5.38 x 1033J
• C. 6.72 x 1033J
• D. 1.35 x 1033J

Explanation

quantity of heat = mass * Specific latent heat → 20 * 336

quantity of heat = 6720j or  6.72 x 1033J

A train of mass 1600 kg attains a speed of 25 ms−1−1 in 20 seconds. The power developed in the engine is?

• A. 2.5 KW
• B. 80 KW
• C. 25 KW
• D. 50 KW

Explanation

where force = f, mass = m, acceleration = a, velocity = v, time = t

Force = m * a → m * ΔvtΔvt

Power = f * v

P = m * vtvt  * v = m * v2tv2t

p =  1600∗252201600∗25220

p = 50,000 or 50 KW

The main factor which affects the speed of sound wave is the?

• A. properties of the medium
• B. amplitude of the sound wave
• C. intensity of the sound wave
• D. loudness of the sound wave

Explanation

Factors Affecting The Speed of Sound

• The Density of Medium: Sound requires a medium to travel. The density of the medium is among the factors which affect the speed of sound. …
• The Temperature of The Medium: Higher the temperature, the higher is the speed of sound in the medium.

A semiconductor is formed by?

• A. co-ordinate bonds
• B. electrovalent bonds
• C. a substance free of bonds
• D. covalent bonds

Explanation

It’s generally created using silicon, germanium, or other pure elements.

Semiconductors are created by adding impurities to the element.

The conductance or inductance of the element depends on the type and intensity of the added impurities.

The electrons surrounding each atom in a semiconductor are part of a covalent bond

One of the following is a scalar quantity?

• A. weight
• B. momentum
• C. potential energy
• D. moments

Explanation

Examples of scalar quantities are mass, distance, charge, volume, time, speed, and the magnitude of physical vectors in general.

The moment of inertia is a scalar quantity.

The mercury column in the barometer at notational  atmospheric pressure has a height of?

• A. 0.76 cm at see level
• B. 760 cm at sea level
• C. 7.6 cm at sea level
• D. 76 cm at sea level

Explanation

The height of the mercury column serves as an indicator of atmospheric pressure. At sea level and at a temperature of 0° Celsius (C), the height of the mercury column is approximately 30 inches, or 76 centimeters. This represents a pressure of approximately 14.7 psia. The 30-inch column is used as a reference standard.

If an object just begins to slide on a surface inclined at 30º to the horizontal,the coefficient of friction is?

• A. √3
• B. √32√32
• C. 1√21√2
• D. 1√31√3

Explanation

A body sliding down a plane inclined at 30o to the horizontal,

Has coefficient of friction = tan 30º  or 1√3

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