Question 1

Which statement correctly describes how chemical reactivity changes down the group for alkali metals and halogens?

Accepted Answer

In alkali metals, reactivity increases, whereas in halogens it decreases as atomic number increases down the group.. This statement is correct because alkali metals become more reactive as they have a greater tendency to lose their outer electron with increasing atomic size, while halogens become less reactive as they have a harder time gaining an electron due to increased distance from the nucleus.

Question 2

Which of the following is a true peroxide?

Accepted Answer

BaO2. BaO2 is a true peroxide because it contains the peroxide ion (O2²-), which is characterized by the presence of an O-O bond. In contrast, the other options do not contain this specific ion structure.

Question 3

When zeolite, a hydrated sodium aluminium silicate, is used with hard water, which ions from the water replace the sodium ions in the zeolite?

Accepted Answer

Ca²⁺ ions. Zeolite acts as an ion exchange material, where the sodium ions are replaced by calcium ions from hard water, effectively softening the water by removing hardness-causing minerals.

Question 4

Among the following carbonates, which one is the least thermally stable?

Accepted Answer

Li2CO3. Lithium carbonate (Li2CO3) is the least thermally stable due to the small size of lithium ions, which leads to stronger lattice energy and makes it more susceptible to decomposition at lower temperatures compared to the other alkali metal carbonates.

Question 5

The solubility of carbonates falls as we move down the magnesium group because there is a reduction in the

Accepted Answer

hydration energy of the cations. As we move down the magnesium group, the cations become larger, which leads to a decrease in their hydration energy. This reduction in hydration energy means that less energy is available to overcome the lattice energy of the solid, resulting in lower solubility of the carbonates.

Question 6

Which of the following salts fails to give any colour in a flame test?

Accepted Answer

MgCl2. MgCl2 does not produce a characteristic color in a flame test because magnesium ions do not emit visible light when heated, unlike the other salts listed which contain elements that do.

Question 7

Which statement about sodium peroxide, Na2O2, is incorrect?

Accepted Answer

It is the superoxide of sodium. The statement is incorrect because sodium peroxide (Na2O2) is not a superoxide; rather, sodium superoxide (NaO2) is the compound that contains the superoxide ion (O2−). Sodium peroxide contains the peroxide ion (O2²−) instead.

Question 8

Each of the following pairs reacts with water. Which pair produces the same gas in both cases?

Accepted Answer

Ca and CaH2. Ca + 2H2O -> Ca(OH)2 + H2 and CaH2 + 2H2O -> Ca(OH)2 + 2H2 both evolve hydrogen. The stored pair K/KO2 gives H2 and O2 respectively (different gases).

Question 9

A substance A, when heated, releases a colourless gas and leaves behind a solid residue. This residue is dissolved in water to form solution B. When carbon dioxide is passed in excess through aqueous B, a solid C is produced and can be collected. On mild heating, solid C regenerates A. Ide

Accepted Answer

CaCO3. Calcium carbonate (CaCO3) decomposes upon heating to release carbon dioxide (CO2) and leave behind calcium oxide (CaO) as a solid residue. When this residue is dissolved in water, it forms a solution that can react with excess CO2 to produce calcium carbonate again, which aligns with the regeneration of A.

Question 10

In the Castner–Kellner process used to manufacture sodium hydroxide, which statement is correct?

Accepted Answer

Sodium amalgam is produced at the mercury cathode. In the Castner–Kellner process, sodium ions are reduced at the mercury cathode to form sodium amalgam, which is a key step in producing sodium hydroxide from brine.

Question 11

Lithium has a melting point of 181°C, which is nearly twice that of sodium at 98°C. This is mainly because

Accepted Answer

as we move down the group, cohesive energy falls. Lithium has a higher melting point than sodium primarily due to its stronger cohesive energy, which is a result of its smaller atomic size and greater charge density, leading to stronger metallic bonding compared to sodium.

Question 12

Which of the following metals does not combine with water even when heated to red heat?

Accepted Answer

Beryllium. Beryllium is a relatively inert metal that does not react with water, even at high temperatures, due to the formation of a protective oxide layer on its surface that prevents further reaction.

Question 13

Which of the following ions occur in biological fluids: Na+, Mg2+, Ca2+, K+, Sr2+, Li+ and Ba2+?

Accepted Answer

Na+, K+, Mg2+ and Ca2+. Na+, K+, Mg2+, and Ca2+ are essential ions that play critical roles in various physiological processes, including nerve transmission, muscle contraction, and maintaining fluid balance in biological systems.

Question 14

Among the sulphates of alkaline earth metals given below, which one has hydration enthalpy greater than lattice enthalpy?

Accepted Answer

BeSO4. BeSO4 has a higher hydration enthalpy than its lattice enthalpy due to the small size and high charge density of beryllium ions, which allows for stronger interactions with water molecules, thus favoring solubility.

Question 15

When metallic sodium is dissolved in liquid ammonia, a deep blue solution is produced. This blue colour arises because of the formation of:

Accepted Answer

solvated electron, e(NH3)x. The deep blue color in the solution is due to the presence of solvated electrons, which are free electrons that become stabilized by the surrounding ammonia molecules, allowing them to absorb specific wavelengths of light.

Question 16

A firework emits a crimson-red flame. Which metal salt is present in it?

Accepted Answer

Strontium. A crimson-red flame is characteristic of strontium salts. Sodium gives a golden-yellow flame, so the stored answer is wrong.

Question 17

Which of the following is a basic oxide of saline nature?

Accepted Answer

Na2O. Na2O is a basic oxide because it is formed from sodium, a metal, and reacts with acids to form salts and water, exhibiting basic properties. Its saline nature comes from its ability to combine with acids to produce neutral salts.

Question 18

The products obtained on heating LiNO3 will be:

Accepted Answer

Li2O + NO2 + O2. Heating lithium nitrate (LiNO3) leads to its decomposition into lithium oxide (Li2O), nitrogen dioxide (NO2), and oxygen (O2), which is consistent with the known thermal decomposition reactions of nitrates.

Question 19

Which one of the following alkaline earth metal sulphates has its hydration enthalpy greater than its lattice enthalpy ?

Accepted Answer

BeSO4. BeSO4 has a higher hydration enthalpy compared to its lattice enthalpy due to the small size and high charge density of the beryllium ion, which allows for stronger interactions with water molecules, leading to greater stabilization upon hydration.

Question 20

The main oxides formed on combustion of Li, Na and K in excess of air are, respectively:

Accepted Answer

Li2O, Na2O2 and KO2. Lithium primarily forms lithium oxide (Li2O) upon combustion, while sodium reacts to form sodium peroxide (Na2O2) due to its ability to stabilize the peroxide ion. Potassium, being more reactive, forms potassium superoxide (KO2) in the presence of excess oxygen.

Question 21

Both lithium and magnesium display several similar properties due to the diagonal relationship; however, the one which is incorrect is:

Accepted Answer

Both form basic carbonates. Lithium and magnesium do share some properties, but lithium carbonate is not basic; it is actually a neutral salt, while magnesium carbonate is basic. This distinction makes the statement about both forming basic carbonates incorrect.

Question 22

The alkaline earth metal nitrate that does not crystallise with water molecules, is:

Accepted Answer

Ba(NO3)2. Barium nitrate is unique among the alkaline earth metal nitrates listed because it does not form a hydrate, meaning it does not incorporate water molecules into its crystalline structure, unlike the others.

Question 23

Magnesium powder burns in air to give:

Accepted Answer

MgO and Mg3N2. When magnesium powder burns in air, it reacts with oxygen to form magnesium oxide (MgO) and can also react with nitrogen present in the air to produce magnesium nitride (Mg3N2), making option B the correct choice.

Question 24

In the following reactions, ZnO is respectively acting as a/an:
(i) ZnO + Na2O → Na2ZnO2
(ii) ZnO + CO2 → ZnCO3

Accepted Answer

acid and base. In the first reaction, ZnO acts as an acid by reacting with the base Na2O to form a zincate, while in the second reaction, ZnO behaves as a base by reacting with CO2 to form zinc carbonate.

Question 25

Which one of the following alkaline earth metal sulphates has its hydration enthalpy greater than its lattice enthalpy?
(1) CaSO4
(2) BeSO4
(3) BaSO4
(4) SrSO4

Accepted Answer

BeSO4. BeSO4 has a high hydration enthalpy due to the small size and high charge density of the Be2+ ion, which allows it to interact strongly with water molecules. This strong interaction results in a hydration enthalpy that exceeds the lattice enthalpy, making it unique among the alkaline earth metal sulfates.

Question 26

In KO2, the nature of oxygen species and the oxidation state of oxygen atom are, respectively:

Accepted Answer

Superoxide and −1/2. In KO2, the oxygen exists as superoxide, which is characterized by the presence of an O2- ion with a charge of -1/2 per oxygen atom. This unique oxidation state arises because the superoxide ion contains a single unpaired electron, leading to its distinct properties.

Question 27

Q.10 Match the following items in column I with the corresponding items in column II.
Column I
(i) Na2CO3.10H2O
(ii) Mg(HCO3)2
(iii) NaOH
(iv) Ca3Al2O6
Column II
(A) Portland cement ingredient
(B) Castner-Kellner process
(C) Solvay process
(D) Temporary hardness

Accepted Answer

(4) (i)→(C); (ii)→(D); (iii)→(B); (iv)→(A). The correct option matches each compound with its appropriate process or classification: Na2CO3.10H2O is produced in the Solvay process, Mg(HCO3)2 is associated with temporary hardness in water, NaOH is produced via the Castner-Kellner process, and Ca3Al2O6 is a key ingredient in Portland cement.

Question 28

Sodium metal on dissolution in liquid ammonia gives a deep blue solution due to the formation of:

Accepted Answer

ammoniated electrons. Sodium in liquid ammonia ionises to give Na+ and free electrons that are solvated by ammonia. These ammoniated electrons absorb in the visible region and give the characteristic deep blue colour.

Question 29

The metal that gives hydrogen gas upon treatment with both acid as well as base is:

Accepted Answer

zinc. Zinc is amphoteric: Zn + 2HCl -> ZnCl2 + H2 and Zn + 2NaOH -> Na2ZnO2 + H2, so it liberates hydrogen with both acids and bases.

Question 30

In comparison to boron, beryllium has:

Accepted Answer

lesser nuclear charge and greater first ionisation enthalpy. Beryllium has a greater nuclear charge than boron due to having more protons, but its first ionization enthalpy is higher because it has a smaller atomic radius and a more stable electron configuration, making it harder to remove an electron.

Question 31

The element with Z = 120 (not yet discovered) will be an/-

Accepted Answer

Alkaline earth metal. Elements with atomic numbers greater than 2 in Group 2 of the periodic table are classified as alkaline earth metals. Since element Z = 120 falls into this group, it is expected to exhibit similar properties to other alkaline earth metals.

Question 32

On combustion Li, Na and K in excess of air, the major oxides formed, respectively, are-

Accepted Answer

Li2O, Na2O2 and KO2. Lithium primarily forms lithium oxide (Li2O) due to its lower reactivity, while sodium reacts to form sodium peroxide (Na2O2) in excess oxygen. Potassium, being more reactive, forms potassium superoxide (KO2) under similar conditions, making option C the correct choice.

Question 33

Among the sulphates of alkaline earth metals, the solubilities of BeSO4 and MgSO4 in water, respectively, are -

Accepted Answer

high and high. Both beryllium sulfate (BeSO4) and magnesium sulfate (MgSO4) are highly soluble in water due to their ionic nature and the ability of water molecules to stabilize the resulting ions.

Question 34

Match the following compounds (Column-I) with their uses (Column-II):
Column-I: (I) Ca(OH)2, (II) NaCl, (III) CaSO4·1/2 H2O, (IV) CaCO3
Column-II: (A) casts of statues, (B) white wash, (C) antacid, (D) washing soda preparation

Accepted Answer

(I)-(B), (II)-(D), (III)-(A), (IV)-(C). Ca(OH)2 is used for white wash (B), NaCl for washing soda preparation (D), CaSO4.1/2H2O (plaster of Paris) for casts of statues (A), and CaCO3 as an antacid (C). So I-B, II-D, III-A, IV-C.

Question 35

A metal (A) on heating in nitrogen gas gives compound B. On treatment with H2O gives a colourless gas which when passed through CuSO4 solution gives a dark blue-violet coloured solution. A and B respectively are:

Accepted Answer

Mg and Mg3N2. When magnesium (Mg) reacts with nitrogen gas, it forms magnesium nitride (Mg3N2). Upon hydrolysis, magnesium nitride produces ammonia and hydrogen gas, the latter of which is colorless and can react with copper sulfate to form a blue solution, confirming that Mg and Mg3N2 are the correct pair.

Question 36

Among the statements (a) – (d), the correct ones are: (a) Lithium has the highest hydration enthalpy among the alkali metals. (b) Lithium chloride is insoluble in pyridine. (c) Lithium cannot form ethynide upon its reaction with ethyne (d) Both lithium and magnesium react slowly with H2O

Accepted Answer

(4) (a), (c) and (d) only. (a) Li has the highest hydration enthalpy among alkali metals (smallest cation) - true. (b) LiCl is actually soluble in pyridine (covalent character) - false. (c) Li does not form an ethynide with ethyne - true. (d) By the diagonal relationship both Li and Mg react slowly with water - true. So (a), (c), (d) are correct.

Question 37

Number of paramagnetic oxides among following given oxides is Li2O, CaO, Na2O, KO2, MgO and K2O

Accepted Answer

1. Among Li2O, CaO, Na2O, KO2, MgO, K2O only KO2 contains the superoxide ion O2- which has one unpaired electron and is paramagnetic; the rest are diamagnetic. Count = 1.

Question 38

Given below are two statements:
Statement I: Both CaCl₂·6H₂O and MgCl₂·8H₂O undergo dehydration on heating.
Statement II: BeO is amphoteric whereas the oxides of other elements in the same group are acidic.
In the light of the above statements, choose the correct answer from the options gi

Accepted Answer

Both statement I and statement II are false. Statement II is false: BeO is amphoteric but MgO, CaO etc. are basic, not acidic. Statement I is false: hydrated MgCl2 on heating hydrolyses to MgO/Mg(OH)Cl + HCl rather than simply dehydrating. Hence both statements are false.

Question 39

Match List-I with List-II
List-I
(a) Ca(OCl)2
(b) CaSO4 · 1/2 H2O
(c) CaO
(d) CaCO3
List-II
(i) Antacid
(ii) Cement
(iii) Bleach
(iv) Plaster of paris
Choose the most appropriate answer from the options given below:

Accepted Answer

a-iii, b-iv, c-i, d-ii. Ca(OCl)2 = bleaching powder (bleach, iii); CaSO4.1/2H2O = Plaster of Paris (iv); CaO neutralises acid (antacid, i); CaCO3 is a cement raw material (ii). So a-iii, b-iv, c-i, d-ii.

Question 40

The chemical that is added to reduce the melting point of the reaction mixture during the extraction of aluminium is:

Accepted Answer

Cryolite. Cryolite is added to the extraction process of aluminum to lower the melting point of the alumina, making the electrolysis process more efficient and energy-saving.

Question 41

A s-block element (M) reacts with oxygen to form an oxide of the formula MO2. The oxide is pale yellow in colour and paramagnetic. The element (M) is:

Accepted Answer

K. Potassium (K) is an s-block element that forms the oxide K2O2, which is pale yellow and exhibits paramagnetism due to the presence of unpaired electrons in its structure. This behavior is characteristic of potassium oxides, distinguishing it from the other options.

Question 42

The correct set from the following in which both pairs are in correct order of melting point is:

Accepted Answer

LiF > LiCl; MgO > NaCl. The correct option indicates that LiF has a higher melting point than LiCl due to stronger ionic bonds in LiF, and MgO has a higher melting point than NaCl because of its greater charge density and stronger ionic interactions.

Question 43

What are the products formed in sequence when excess of CO2 is passed in slaked lime?

Accepted Answer

(CaCO3, Ca(HCO3)2). When excess carbon dioxide is passed through slaked lime (calcium hydroxide), it first reacts to form calcium carbonate, which can then further react with additional CO2 to form calcium bicarbonate, making the sequence CaCO3 followed by Ca(HCO3)2.

Question 44

The number of water molecules in gypsum, dead burnt plaster and plaster of paris, respectively are:

Accepted Answer

2, 0 and 0.5. Gypsum contains two water molecules in its chemical structure, while dead burnt plaster has no water molecules as it is an anhydrous form. Plaster of Paris, which is a partially dehydrated form of gypsum, contains half a water molecule in its formula.

Question 45

Match List - I with List - II:
List - I
(a) NaOH
(b) Be(OH)2
(c) Ca(OH)2
(d) B(OH)3
(e) Al(OH)3
List - II
(i) Acidic
(ii) Basic
(iii) Amphoteric
Choose the most appropriate answer from the options given below:

Accepted Answer

(a)-(ii), (b)-(iii), (c)-(ii), (d)-(i), (e)-(iii). NaOH and Ca(OH)2 are basic (ii); Be(OH)2 and Al(OH)3 are amphoteric (iii); B(OH)3 is a Lewis acid, i.e. acidic (i). So a-ii, b-iii, c-ii, d-i, e-iii.

Question 46

Given below are two statements: One is labelled as Assertion A and the other labelled as Reason R.
Assertion A: Lithium halides are some what covalent in nature.
Reason R: Lithium possess high polarisation capability.
In the light of the above statements, choose the most appropriate answer

Accepted Answer

Both A and R are true and R is the correct explanation of A. Lithium halides have appreciable covalent character because the very small Li+ ion has high polarising capability, distorting the halide electron cloud (Fajans' rules). Both A and R are true and R is the correct explanation of A (index 3).

Question 47

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Lithium salts are hydrated. Reason (R): Lithium has higher polarizing power than other alkali metal group members. In the light of the above statements, choose the most

Accepted Answer

Both (A) and (R) are correct and (R) is the correct explanation of (A).. Lithium ion is very small with high charge density, giving it the highest polarizing power among alkali metals, so its salts (e.g. LiCl*H2O) are commonly hydrated. Both (A) and (R) are correct and (R) is the correct explanation of (A).

Question 48

Given below are two statements:
Statement I: None of the alkaline earth metal hydroxides dissolve in alkali.
Statement II: Solubility of alkaline earth metal hydroxides in water increases down the group.
In the light of the above statements, choose the most appropriate answer from the opti

Accepted Answer

Statement I is incorrect but Statement II is correct.. Statement I is incorrect because some alkaline earth metal hydroxides, such as those of calcium, strontium, and barium, do dissolve in water to varying degrees. Statement II is correct as the solubility of these hydroxides does indeed increase as you move down the group in the periodic table.

Question 49

Which of the following statements are correct?
(A) Both LiCl and MgCl2 are soluble in ethanol.
(B) The oxides Li2O and MgO combine with excess of oxygen to give superoxide.
(C) LiF is less soluble in water than other alkali metal fluorides.
(D) Li2O is more soluble in water than other alka

Accepted Answer

(A) and (C) only. (A) LiCl and MgCl2 are covalent enough to dissolve in ethanol - true. (C) LiF has very high lattice energy and is only sparingly soluble - true. (B) Li and Mg form normal oxides, not superoxides - false. (D) Li2O is the least soluble alkali metal oxide, not the most - false. So (A) and (C) only.

Question 50

In the flame test of a mixture of salts, a green flame with blue centre was observed. Which one of the following cations may be present?

Accepted Answer

Cu2+. A green flame with a blue centre is characteristic of copper, so Cu2+ is present. Ca2+ gives a brick-red flame, Sr2+ crimson, and Ba2+ apple-green without the blue centre.

JEE Main Chemistry: The s-Block Elements questions with solutions

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