Chemistry MCQs

Question #981

Consider the following statements: 1. Chromatography separates components based on differential adsorption. 2. The component that is more strongly adsorbed moves faster. Which statement(s) is/are correct?

A. Neither 1 nor 2

B. Both 1 and 2

C. 2 only

D. 1 only

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Correct Answer: Option D

Explanation:
Chromatography is an advanced technique used to separate mixtures based on the differential adsorption of components onto a stationary phase. The component that is more strongly adsorbed to the stationary phase moves slower, not faster. Therefore, only statement 1 is correct, making option A the right choice.

This question belongs to: Science chemistry

Question #982

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The separation of two liquids with a boiling point difference of less than 25 K is best achieved by:

A. Vacuum distillation

B. Steam distillation

C. Simple distillation

D. Fractional distillation

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Correct Answer: Option D

Explanation:
Fractional distillation is specifically designed to separate miscible liquids whose boiling points differ by less than 25 K. It uses a fractionating column which provides surfaces for repeated evaporation and condensation, enriching the vapor with the more volatile component before it reaches the condenser.

This question belongs to: Science chemistry

Question #983

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Which of the following is an example of a gel?

A. Fog

B. Milk

C. Cheese

D. Smoke

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Correct Answer: Option C

Explanation:
A gel is a type of colloid where the dispersed phase is a liquid and the dispersed medium is a solid. Cheese, butter, and jellies are classic examples of gels. Milk is an emulsion (liquid in liquid), while fog and smoke are aerosols.

This question belongs to: Science chemistry

Question #984

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Assertion (A): The mass of an atom is concentrated in the nucleus. Reason (R): Protons and neutrons are present inside the nucleus.

A. Both A and R are true and R is the correct explanation of A.

B. Both A and R are true but R is NOT the correct explanation of A.

C. A is true but R is false.

D. A is false but R is true.

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Correct Answer: Option A

Explanation:
The mass of an atom is almost entirely concentrated in its tiny central nucleus. This is because the nucleus contains protons and neutrons, which are much heavier than the extranuclear electrons. Since electrons have negligible mass, R correctly explains why the mass is localized in the nucleus.

This question belongs to: Science chemistry

Question #985

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Which of the following isotopes is used in the treatment of blood cancers?

A. Carbon-14

B. Iodine-131

C. Cobalt-60

D. Sodium-24

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Correct Answer: Option C

Explanation:
Cobalt-60 is a radioactive isotope that emits strong gamma radiation. It is widely used in radiotherapy to treat various types of cancers, including blood cancers like leukemia. Iodine-131 is used for thyroid disorders, Carbon-14 for radiocarbon dating, and Sodium-24 for detecting blood clots.

This question belongs to: Science chemistry

Question #986

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Which of the following sets of quantum numbers is impossible?

A. n=3, l=2, m=-3, s=+1/2

B. n=1, l=0, m=0, s=+1/2

C. n=4, l=3, m=0, s=-1/2

D. n=2, l=1, m=-1, s=-1/2

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Correct Answer: Option A

Explanation:
The magnetic quantum number (m) can only take integer values ranging from -l to +l. For n=3, l can be 2 (a d-orbital). If l=2, the possible values for m are -2, -1, 0, +1, +2. The value m=-3 is outside this range, making this set of quantum numbers impossible.

This question belongs to: Science chemistry

Question #987

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Consider the following statements regarding cathode rays: 1. They originate from the cathode. 2. They are made of electromagnetic waves. 3. They cast shadows. Which are correct?

A. 1 and 3 only

B. 2 and 3 only

C. 1, 2 and 3

D. 1 and 2 only

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Correct Answer: Option A

Explanation:
Cathode rays are streams of fast-moving electrons, not electromagnetic waves, originating from the cathode in a discharge tube. Because they are material particles traveling in straight lines, they can be stopped by opaque objects, thus casting sharp shadows. Therefore, statements 1 and 3 are correct.

This question belongs to: Science chemistry

Question #988

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The maximum number of electrons that can be associated with the quantum numbers n=3, l=1, m=-1 is:

A. 10

B. 6

C. 2

D. 1

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Correct Answer: Option C

Explanation:
The quantum numbers n=3 and l=1 specify the 3p subshell. The magnetic quantum number m=-1 specifies one particular 3p orbital within that subshell. According to Pauli's Exclusion Principle, a single orbital can accommodate a maximum of two electrons, which must have opposite spins (+1/2 and -1/2).

This question belongs to: Science chemistry

Question #989

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Which of the following molecules has a net dipole moment of zero due to its geometry?

A. NF3

B. ClF3

C. H2S

D. BF3

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Correct Answer: Option D

Explanation:
BF3 has a trigonal planar geometry with bond angles of 120 degrees. The three B-F bond dipoles are equal in magnitude and symmetrically arranged, so their vector sum cancels out completely, resulting in a net dipole moment of zero. H2S is bent, NF3 is pyramidal, and ClF3 is T-shaped.

This question belongs to: Science chemistry

Question #990

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Assertion (A): HF has an unusually high boiling point. Reason (R): Fluorine is the most electronegative element, leading to strong hydrogen bonding in HF.

A. A is false but R is true.

B. A is true but R is false.

C. Both A and R are true and R is the correct explanation of A.

D. Both A and R are true but R is NOT the correct explanation of A.

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Correct Answer: Option C

Explanation:
HF exhibits strong intermolecular hydrogen bonding because fluorine is highly electronegative and small in size. This strong hydrogen bonding requires significantly more thermal energy to break compared to other hydrogen halides, giving HF an unusually high boiling point. Both statements are true and R correctly explains A.

This question belongs to: Science chemistry

Question #991

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Which of the following compounds contains both ionic and covalent bonds?

A. AlCl3

B. K2O

C. MgCl2

D. NH4Cl

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Correct Answer: Option D

Explanation:
Ammonium chloride (NH4Cl) consists of the ammonium ion (NH4+) and the chloride ion (Cl-). The bond between NH4+ and Cl- is ionic. However, within the ammonium ion itself, the nitrogen atom is bonded to four hydrogen atoms via covalent bonds (three normal and one coordinate). Thus, it contains both.

This question belongs to: Science chemistry

Question #992

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According to Fajan's rules, which of the following conditions favors the formation of a covalent bond?

A. Large cation and small anion

B. Large cation and large anion

C. Small cation and small anion

D. Small cation and large anion

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Correct Answer: Option D

Explanation:
Fajan's rules state that covalent character in an ionic bond increases with greater polarizing power of the cation and greater polarizability of the anion. A small cation has high charge density (high polarizing power), and a large anion has loosely held outer electrons (high polarizability), favoring covalency.

This question belongs to: Science chemistry

Question #993

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Which of the following species is isoelectronic with CO?

A. CO2

B. N2

C. NO

D. O2

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Correct Answer: Option B

Explanation:
Isoelectronic species have the same total number of electrons. Carbon monoxide (CO) has 6 (from C) + 8 (from O) = 14 electrons. Nitrogen molecule (N2) has 7 + 7 = 14 electrons. Therefore, N2 is isoelectronic with CO. O2 has 16, CO2 has 22, and NO has 15 electrons.

This question belongs to: Science chemistry

Question #994

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The hybridization of the central atom in the sulfate ion (SO4 2-) is:

A. sp3d

B. sp2

C. sp

D. sp3

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Correct Answer: Option D

Explanation:
In the sulfate ion (SO4 2-), the central sulfur atom is bonded to four oxygen atoms with no lone pairs on the sulfur. The steric number is 4 (4 sigma bonds + 0 lone pairs). A steric number of 4 corresponds to sp3 hybridization, resulting in a tetrahedral geometry.

This question belongs to: Science chemistry

Question #995

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Which of the following statements is incorrect regarding metallic bonds?

A. They are highly directional in nature.

B. They involve a sea of delocalized electrons.

C. They are responsible for the high electrical conductivity of metals.

D. They explain the malleability and ductility of metals.

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Correct Answer: Option A

Explanation:
Metallic bonds are formed by the electrostatic attraction between positive metal ions and a 'sea' of delocalized valence electrons. These bonds are non-directional, which allows the metal ions to slide past one another without breaking the bond, explaining malleability and ductility. Therefore, statement C is incorrect.

This question belongs to: Science chemistry

Question #996

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Consider the following statements: 1. Lattice energy increases with an increase in the charge of the ions. 2. Lattice energy decreases with an increase in the size of the ions. Which is/are correct?

A. Both 1 and 2

B. 2 only

C. Neither 1 nor 2

D. 1 only

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Correct Answer: Option A

Explanation:
Lattice energy is the energy required to separate one mole of an ionic solid into its gaseous ions. According to Coulomb's law, it is directly proportional to the product of the ionic charges and inversely proportional to the sum of their radii. Thus, higher charges and smaller sizes both increase lattice energy.

This question belongs to: Science chemistry

Question #997

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The geometry and magnetic nature of the [Ni(CN)4]2- complex is:

A. Tetrahedral, diamagnetic

B. Tetrahedral, paramagnetic

C. Square planar, diamagnetic

D. Square planar, paramagnetic

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Correct Answer: Option C

Explanation:
In [Ni(CN)4]2-, Ni is in the +2 oxidation state (d8 configuration). CN- is a strong field ligand, causing the pairing of d-electrons. This leaves one empty d-orbital, leading to dsp2 hybridization. The geometry is square planar. Since all electrons are paired, the complex is diamagnetic.

This question belongs to: Science chemistry

Question #998

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Which of the following elements has the highest second ionization energy?

A. Aluminum

B. Sodium

C. Magnesium

D. Silicon

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Correct Answer: Option B

Explanation:
Sodium has the electronic configuration [Ne]3s1. After losing one electron to form Na+, it achieves a highly stable noble gas configuration ([Ne]). Removing a second electron from this stable core requires an exceptionally large amount of energy. Thus, sodium has the highest second ionization energy among these elements.

This question belongs to: Science chemistry

Question #999

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The diagonal relationship in the periodic table is most prominently seen between:

A. All of the above

B. Beryllium and Aluminum

C. Lithium and Magnesium

D. Boron and Silicon

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Correct Answer: Option A

Explanation:
The diagonal relationship occurs when elements in the second period resemble elements in the third period of the next group due to similar ionic sizes and charge-to-radius ratios (polarizing power). Li-Mg, Be-Al, and B-Si are all classic examples of this phenomenon.

This question belongs to: Science chemistry

Question #1000

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Which of the following orders of atomic radii is correct?

A. I > Br > F > Cl

B. Na > Mg > Al > Si

C. F > Cl > Br > I

D. O > N > C > B

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Correct Answer: Option B

Explanation:
Across a period from left to right, atomic radius decreases due to increasing effective nuclear charge. Therefore, the correct order for period 3 elements is Na > Mg > Al > Si. Down a group, radius increases, so F < Cl < Br < I. Options A, C, and D have incorrect trends.

This question belongs to: Science chemistry

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