Question 1

Amongst the following, the total number of species NOT having eight electrons around central atom in its outer most shell, is

NH₃, AlCl₃, BeCl₂, CCl₄, PCl₅

Accepted Answer

3. Counting the electrons around the central atom:

NH₃ — 8 (octet complete)
AlCl₃ — 6, electron deficient
BeCl₂ — 4, electron deficient
CCl₄ — 8 (octet complete)
PCl₅ — 10, an expanded octet

So three species (AlCl₃, BeCl₂ and PCl₅) do not have eight electrons.

Question 2

Some tranquilizers are listed below. Which one from the following belongs to barbiturates?

Accepted Answer

Veronal. Veronal, amytal, nembutal, luminal and seconal are all derivatives of barbituric acid — the barbiturates, an important class of tranquilizers.

Valium and chlordiazepoxide are benzodiazepines, and meprobamate is a carbamate.

Question 3

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: A reaction can have zero activation energy.
Reason R: The minimum extra amount of energy absorbed by reactant molecules so that their energy becomes equal to threshold value, is called activation energy.

In the light of the above statements, choose the correct answer from the options given below:

Accepted Answer

Both A and R are true and R is NOT the correct explanation of A.. Both statements are true. A reaction CAN have zero activation energy, when the reactant molecules already possess the threshold energy.

And the Reason correctly defines activation energy as the minimum extra energy that must be absorbed to reach the threshold.

But the definition does not by itself explain why a zero-activation-energy reaction is possible, so R is not the correct explanation of A.

Question 4

The given compound is an example of:

Accepted Answer

allylic halide. In an allylic halide the halogen is attached to an sp^3 carbon which is next to a carbon-carbon double bond.

Here X sits on the sp^3 carbon adjacent to the CH=CH double bond, so the compound is an allylic halide.

Question 5

The number of \sigma bonds, \pi bonds and lone pair of electrons in pyridine, respectively, are:

Accepted Answer

11, 3, 1. Pyridine, \ce{C5H5N}, is a six-membered aromatic ring with five C−H bonds.

Ring bonds: 6 sigma; C−H bonds: 5 sigma — giving 11 \sigma bonds in all.
The aromatic ring has 3 \pi bonds.
The nitrogen carries 1 lone pair, which lies in the ring plane and is not part of the aromatic sextet.

Question 6

The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40)

\ce{CaCO3 ->[1200 K] CaO + CO2}

Accepted Answer

1.76 g. 100 g of CaCO₃ gives 44 g of CO₂.

For 20 g of pure CaCO₃: \dfrac{20}{100} 	imes 44 = 8.8\ 	ext{g} of CO₂.

But the limestone is only 20% pure, so:

\dfrac{20}{100} 	imes 8.8 = 1.76\ 	ext{g}

Question 7

Which one is an example of heterogenous catalysis?

Accepted Answer

Combination between dinitrogen and dihydrogen to form ammonia in the presence of finely divided iron.. In heterogeneous catalysis the catalyst is in a DIFFERENT phase from the reactants.

\ce{N2(g) + 3H2(g) ->[Fe(s)] 2NH3(g)} — the gases react over a solid iron catalyst, so the phases differ. This is the Haber process.

The other three all have catalyst and reactants in the same phase.

Question 8

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: Metallic sodium dissolves in liquid ammonia giving a deep blue solution, which is paramagnetic.
Reason R: The deep blue solution is due to the formation of amide.

In the light of the above statements, choose the correct answer from the options given below.

Accepted Answer

A is true but R is false. The Assertion is true — alkali metals dissolve in liquid ammonia to give deep blue, paramagnetic solutions.

The Reason is false: the blue colour is due to AMMONIATED ELECTRONS, not to the formation of an amide. The ammoniated electron is also what makes the solution paramagnetic.

Question 9

Which one of the following statements is correct?

Accepted Answer

The daily requirement of Mg and Ca in the human body is estimated to be 0.2 - 0.3 g.. The daily requirement of magnesium and calcium in the human body is about 200–300 mg, i.e. 0.2–0.3 g — statement (c) is correct.

The others are wrong: bone is a dynamic, constantly remodelled tissue; it is CALCIUM that plays the role in neuromuscular function and interneuronal transmission; and enzymes using ATP in phosphate transfer require MAGNESIUM as the cofactor.

Question 10

Identify the product in the following reactions:

Accepted Answer

. Step (i) \ce{Cu2Br2}/HBr is a Sandmeyer-type reaction: the diazonium group is replaced by bromine, giving bromobenzene.

Step (ii) Mg in dry ether forms the Grignard reagent, phenylmagnesium bromide.

Step (iii) water protonates the Grignard reagent, replacing \ce{-MgBr} by \ce{-H}.

The product is therefore plain benzene.

Question 11

For a certain reaction, the rate = k[A]^2[B]. When the initial concentration of A is tripled keeping concentration of B constant, the initial rate would:

Accepted Answer

Increase by a factor of nine. The rate is second order in A, so with [B] fixed the rate goes as [A]^2.

\dfrac{r_f}{r_i} = \dfrac{(3[A])^2}{[A]^2} = 9

So the rate increases by a factor of nine.

Question 12

Which of the following statements are NOT correct?

A. hydrogen is used to reduce heavy metal oxides to metal.
B. heavy water is used to study reaction mechanism.
C. hydrogen is used to make saturated fats from oils
D. The H−H bond dissociation enthalpy is lowest as compared to a single bond between two atoms of any element.
E. Hydrogen reduces oxides of metals that are more active than iron.

Choose the most appropriate answer from the options given below:

Accepted Answer

D, E only. D is wrong: because of the small size of the hydrogen atoms the s–s overlap is very effective, so the H−H bond dissociation enthalpy is the HIGHEST for a single bond between two atoms of any element, not the lowest.

E is wrong: hydrogen only reduces the oxides of metals that are LESS active than iron. Metals above iron in the reactivity series are not reduced by it.

A, B and C are all correct.

Question 13

Homoleptic complex from the following complexes is:

Accepted Answer

Potassium trixalatoaluminate (III). A homoleptic complex is bound to only ONE kind of ligand.

Potassium trioxalatoaluminate(III) is \ce{K3[Al(C2O4)3]} — the aluminium is surrounded by three oxalate ligands and nothing else, so it is homoleptic.

Each of the others carries two or more different ligands.

Question 14

In Lassaigne's extract of an organic compound both nitrogen and sulphur are present, which gives red colour with Fe³⁺ due to formation of

Accepted Answer

\ce{[Fe(SCN)]^2+}. When both nitrogen and sulphur are present, sodium fusion gives sodium thiocyanate:

\ce{Na + C + N + S -> NaSCN}

The thiocyanate then reacts with ferric ion to give the blood-red complex:

\ce{Fe^3+ + SCN^- -> [Fe(SCN)]^2+}

Question 15

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: In equation \Delta_r G = -nFE_{cell} value of \Delta_r G depends on n.
Reason R: E_{cell} is an intensive property and \Delta_r G is an extensive property.

In the light of the above statements, choose the correct answer from the options given below:

Accepted Answer

Both A and R are true and R is the correct explanation of A.. Both are true, and the Reason explains the Assertion.

E_{cell} is an intensive property — it does not depend on how much substance reacts. \Delta_r G is extensive, so it scales with the amount, i.e. with n.

That is exactly why \Delta_r G = -nFE_{cell} carries the factor n while E_{cell} does not.

Question 16

Identify product (A) in the following reaction:

Accepted Answer

. Zn–Hg with concentrated HCl is the Clemmensen reduction: it converts a keto group \ce{C=O} all the way to a methylene group \ce{CH2}.

Both acetyl groups are reduced, so each \ce{-CO-CH3} becomes \ce{-CH2-CH3} — giving the di-ethyl compound of option (c), with the two water molecules released as shown.

Question 17

The relation between n_m (n_m = the number of permissible values of magnetic quantum number (m)) for a given value of azimuthal quantum number (l), is:

Accepted Answer

l = \dfrac{n_m - 1}{2}. For a given l, the magnetic quantum number runs from -l to +l, giving

n_m = 2l + 1

Rearranging: 2l = n_m - 1, so l = \dfrac{n_m - 1}{2}.

Question 18

The stability of Cu²⁺ is more than Cu⁺ salts in aqueous solution due to:

Accepted Answer

hydration energy. Cu²⁺ is smaller and doubly charged, and hydration enthalpy goes as \dfrac{	ext{charge}}{	ext{size}}.

So the much larger hydration energy of Cu²⁺ more than compensates for the second ionisation enthalpy, making Cu²⁺ the more stable ion in aqueous solution.

Question 19

Match LIST-I with LIST-II:

LIST-I
(A) Coke
(B) Diamond
(C) Fullerene
(D) Graphite

LIST-II
(I) Carbon atoms are sp^3 hybridised.
(II) Used as a dry lubricant
(III) Used as a reducing Agent
(IV) Cage like molecules

Choose the correct answer from the options given below:

Accepted Answer

A - III, B - I, C - IV, D - II. Coke — used as a reducing agent in metallurgy (III).
Diamond — every carbon is sp^3 hybridised (I).
Fullerene — cage-like molecules such as \ce{C60} (IV).
Graphite — used as a dry lubricant, because its layers slide over one another (II).

Question 20

Weight (g) of two moles of the organic compound which is obtained by heating sodium ethanoate with sodium hydroxide in presence of calcium oxide is:

Accepted Answer

32. This is decarboxylation (soda-lime reaction):

\ce{2CH3COONa + 2NaOH ->[CaO,\ heat] 2CH4 + 2Na2CO3}

The organic product is methane, molar mass 16.

Two moles weigh 2 	imes 16 = 32\ 	ext{g}.

Chemistry — NEET Complete Yearwise Papers MCQs with Solutions

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