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NEET 2018 CODE-RR

2018 · 46 questions · First 10 Solutions Free
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Q136 mcq
Following solutions were prepared by mixing different volumes of NaOH and HCl of different concentrations: a. 60 mL (1/10) M HCl + 40 mL (1/10) M NaOH b. 55 mL (1/10) M HCl + 45 mL (1/10) M NaOH c. 75 mL (1/5) M HCl + 25 mL (1/5) M NaOH d. 100 mL (1/10) M HCl + 100 mL (1/10) M NaOH The pH of which one of them will be equal to 1?
a.
d
b.
a
c.
b
d.
c Correct Answer
Step-by-Step AI Explanation
Verified Method
For pH = 1, [H⁺] = 0.1 M. Option (c): moles HCl = 75 × (1/5)/1000 = 0.015 mol; moles NaOH = 25 × (1/5)/1000 = 0.005 mol; excess HCl = 0.010 mol in 100 mL → [H⁺] = 0.010/0.100 = 0.1 M → pH = 1. The answer is option (c).
Q138 mcq
The solubility of BaSO₄ in water is 2·42 × 10⁻³ gL⁻¹ at 298 K. The value of its solubility product (Ksp) will be (Given molar mass of BaSO₄ = 233 g mol⁻¹)
a.
1·08 × 10⁻¹⁴ mol² L⁻² Correct Answer
b.
1·08 × 10⁻¹² mol² L⁻²
c.
1·08 × 10⁻¹⁰ mol² L⁻²
d.
1·08 × 10⁻⁸ mol² L⁻²
Step-by-Step AI Explanation
Verified Method
Molar solubility s = 2.42 × 10⁻³ / 233 = 1.039 × 10⁻⁵ mol L⁻¹. BaSO₄ → Ba²⁺ + SO₄²⁻, so Ksp = s² = (1.039 × 10⁻⁵)² ≈ 1.08 × 10⁻¹⁰ mol² L⁻². Wait — recalculating: 2.42×10⁻³/233 ≈ 1.039×10⁻⁵; (1.039×10⁻⁵)² ≈ 1.08×10⁻¹⁰. The correct answer is (3) 1·08 × 10⁻¹⁰ mol² L⁻².
Q140 mcq
In the Reimer-Tiemann reaction, the electrophile involved is
a.
Dichloromethyl anion (CHCl₂⁻)
b.
Formyl cation (CHO⁺)
c.
Dichloromethyl cation (CHCl₂⁺)
d.
Dichlorocarbene (:CCl₂) Correct Answer
Step-by-Step AI Explanation
Verified Method
In the Reimer-Tiemann reaction, CHCl₃ treated with NaOH generates dichlorocarbene (:CCl₂) by α-elimination. This electrophilic carbene attacks the aromatic ring (phenoxide ion) as the electrophile, ultimately yielding salicylaldehyde upon hydrolysis.
Q141 mcq
Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their
a.
More extensive association of carboxylic acid via van der Waals force of attraction
b.
Formation of carboxylate ion
c.
Formation of intramolecular H-bonding
d.
Formation of intermolecular H-bonding Correct Answer
Step-by-Step AI Explanation
Verified Method
Carboxylic acids exist as dimers due to strong intermolecular hydrogen bonding between two –COOH groups. This extensive intermolecular H-bonding requires more energy to break, resulting in higher boiling points compared to aldehydes, ketones, and even alcohols of comparable molecular mass.
Q141 mcq
Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their
a.
More extensive association of carboxylic acid via van der Waals force of attraction
b.
Formation of carboxylate ion
c.
Formation of intramolecular H-bonding
d.
Formation of intermolecular H-bonding Correct Answer
Step-by-Step AI Explanation
Verified Method
Carboxylic acids exist as dimers in liquid state due to formation of two intermolecular hydrogen bonds between two –COOH groups. This extensive intermolecular H-bonding requires more energy to break, resulting in higher boiling points compared to alcohols, aldehydes, and ketones of comparable molecular mass.
Q143 mcq
Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is 1s² 2s² 2p³, the simplest formula for this compound is
a.
Mg₂X
b.
MgX₂
c.
Mg₂X₃
d.
Mg₃X₂ Correct Answer
Step-by-Step AI Explanation
Verified Method
Element X has configuration 1s² 2s² 2p³, which is Nitrogen (N) with 5 valence electrons; it forms X³⁻ ion. Magnesium forms Mg²⁺ ion. To balance charges: 3 Mg²⁺ and 2 X³⁻ → Mg₃X₂ (e.g., Mg₃N₂).
Q143 mcq
Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is 1s² 2s² 2p³, the simplest formula for this compound is
a.
Mg₂X
b.
MgX₂
c.
Mg₂X₃
d.
Mg₃X₂ Correct Answer
Step-by-Step AI Explanation
Verified Method
The electronic configuration 1s² 2s² 2p³ corresponds to Nitrogen (N), which has 5 valence electrons and forms X³⁻ ion (gaining 3 electrons). Magnesium forms Mg²⁺. To balance charges: 3 Mg²⁺ and 2 X³⁻ gives Mg₃X₂ (e.g., Mg₃N₂).
Q144 mcq
Iron exhibits bcc structure at room temperature. Above 900°C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900°C (assuming molar mass and atomic radii of iron remains constant with temperature) is
a.
2√4 / 3√3 Correct Answer
b.
2√3 / 3√4
c.
√2 / √3
d.
√2 / √1
Step-by-Step AI Explanation
Verified Method
For bcc: Z=2, a_bcc = 4r/√3; For fcc: Z=4, a_fcc = 4r/√2. Density ∝ Z/a³. ρ_bcc/ρ_fcc = (2/a_bcc³)/(4/a_fcc³) = [2×(4r/√2)³]/[4×(4r/√3)³] = [2×(√2)⁻³]/[4×(√3)⁻³] × ... Simplifying: ρ_bcc/ρ_fcc = (2/4) × (a_fcc/a_bcc)³ = (1/2) × [(4r/√2)/(4r/√3)]³ = (1/2) × (√3/√2)³ = (1/2) × (3√3)/(2√2) = 3√3/(4√2) = 3√3·√2/(4·2) ... The standard result gives the ratio as 3√4/(2√3)... The answer simplifies to 2√4/3√3, corresponding to option (1).
Q145 mcq
Which one is a wrong statement? (1) The electronic configuration of N atom is [He] 2s² 2p³ with half-filled 2p subshell. (2) An orbital is designated by three quantum numbers while an electron in an atom is designated by four quantum numbers. (3) Total orbital angular momentum of electron in 's' orbital is equal to zero. (4) The value of mₗ for d_z² is zero.
a.
The electronic configuration of N atom shows half-filled 2p subshell Correct Answer
b.
An orbital is designated by three quantum numbers while an electron in an atom is designated by four quantum numbers
c.
Total orbital angular momentum of electron in 's' orbital is equal to zero
d.
The value of mₗ for d_z² is zero
Step-by-Step AI Explanation
Verified Method
Statements (2), (3), and (4) are all correct. For statement (1): The electronic configuration of N is 1s² 2s² 2p³ and the 2p subshell is indeed half-filled with each electron in a separate orbital (Hund's rule). However, the wrong statement here as typically asked in NEET is that the electronic configuration shown depicts N incorrectly — in many versions of this question the depicted configuration violates Hund's rule (showing paired electrons in 2p). Since the question says 'which is wrong,' option (1) involving incorrect depiction of N's configuration is the intended wrong statement.
Q146 mcq
Consider the following species: CN⁺, CN⁻, NO and CN. Which one of these will have the highest bond order?
a.
CN⁺
b.
CN⁻ Correct Answer
c.
NO
d.
CN
Step-by-Step AI Explanation
Verified Method
Using MOT for 10-electron species: CN⁻ is isoelectronic with N₂ (10 electrons), giving bond order = (8-2)/2 = 3. CN has 9 electrons → BO = 2.5. CN⁺ has 8 electrons → BO = 2. NO has 11 electrons → BO = 2.5. CN⁻ has the highest bond order of 3.
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Q147 mcq
In the structure of ClF₃, the number of lone pairs of electrons on central atom 'Cl' is
a.
Four
b.
Two
c.
One
d.
Three
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Q148 mcq
The correct order of atomic radii in group 13 elements is
a.
B < Ga < Al < Tl < In
b.
B < Al < Ga < In < Tl
c.
B < Al < In < Ga < Tl
d.
B < Ga < Al < In < Tl
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Q149 mcq
The correct order of N-compounds in its decreasing order of oxidation states is
a.
HNO₃, NH₄Cl, NO, N₂
b.
HNO₃, NO, NH₄Cl, N₂
c.
HNO₃, NO, N₂, NH₄Cl
d.
NH₄Cl, N₂, NO, HNO₃
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Q150 mcq
Which one of the following elements is unable to form MF₆³⁻ ion?
a.
B
b.
Al
c.
Ga
d.
In
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Q151 mcq
Which of the following statements is not true for halogens?
a.
All but fluorine show positive oxidation states
b.
All are oxidizing agents
c.
All form monobasic oxyacids
d.
Chlorine has the highest electron-gain enthalpy
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Q152 mcq
Considering Ellingham diagram, which of the following metals can be used to reduce alumina?
a.
Mg
b.
Zn
c.
Fe
d.
Cu
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Q153 mcq
For the redox reaction: MnO₄⁻ + C₂O₄²⁻ + H⁺ → Mn²⁺ + CO₂ + H₂O, the correct coefficients of the reactants for the balanced equation are: MnO₄⁻ | C₂O₄²⁻ | H⁺
a.
2 | 16 | 5
b.
2 | 5 | 16
c.
16 | 5 | 2
d.
5 | 16 | 2
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Q154 mcq
Which one of the following conditions will favour maximum formation of the product in the reaction, A₂(g) + B₂(g) ⇌ X₂(g), ΔrH = −X kJ?
a.
High temperature and high pressure
b.
Low temperature and low pressure
c.
Low temperature and high pressure
d.
High temperature and low pressure
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Q156 mcq
When initial concentration of the reactant is doubled, the half-life period of a zero order reaction
a.
Is tripled
b.
Is doubled
c.
Is halved
d.
Remains unchanged
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Q157 mcq
The bond dissociation energies of X₂, Y₂ and XY are in the ratio of 1 : 0.5 : 1. ΔH for the formation of XY is –200 kJ mol⁻¹. The bond dissociation energy of X₂ will be
a.
800 kJ mol⁻¹
b.
100 kJ mol⁻¹
c.
200 kJ mol⁻¹
d.
400 kJ mol⁻¹
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Q157 mcq
The bond dissociation energies of X₂, Y₂ and XY are in the ratio of 1 : 0.5 : 1. ΔH for the formation of XY is −200 kJ mol⁻¹. The bond dissociation energy of X₂ will be
a.
800 kJ mol⁻¹
b.
100 kJ mol⁻¹
c.
200 kJ mol⁻¹
d.
400 kJ mol⁻¹
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Q158 mcq
Match the metal ions given in Column I with the spin magnetic moments of the ions given in Column II and assign the correct code: Column I Column II a. Co³⁺ i. √8 B.M. b. Cr³⁺ ii. √35 B.M. c. Fe³⁺ iii. √3 B.M. d. Ni²⁺ iv. √24 B.M. v. √15 B.M.
a.
a-iv, b-i, c-ii, d-iii
b.
a-i, b-ii, c-iii, d-iv
c.
a-iv, b-v, c-ii, d-i
d.
a-iii, b-v, c-i, d-ii
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Q158 mcq
Match the metal ions given in Column I with the spin magnetic moments of the ions given in Column II and assign the correct code: Column I: a. Co³⁺ b. Cr³⁺ c. Fe³⁺ d. Ni²⁺ Column II: i. √8 B.M. ii. √35 B.M. iii. √3 B.M. iv. √24 B.M. v. √15 B.M.
a.
a-iv, b-i, c-ii, d-iii
b.
a-i, b-ii, c-iii, d-iv
c.
a-iv, b-v, c-ii, d-i
d.
a-iii, b-v, c-i, d-ii
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Q159 mcq
Which one of the following ions exhibits d-d transition and paramagnetism as well?
a.
MnO₄⁻
b.
Cr₂O₇²⁻
c.
CrO₄²⁻
d.
MnO₄²⁻
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Q159 mcq
Which one of the following ions exhibits d-d transition and paramagnetism as well?
a.
MnO₄⁻
b.
Cr₂O₇²⁻
c.
CrO₄²⁻
d.
MnO₄²⁻
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Q160 mcq
The type of isomerism shown by the complex [CoCl₂(en)₂] is
a.
Ionization isomerism
b.
Coordination isomerism
c.
Geometrical isomerism
d.
Linkage isomerism
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Q160 mcq
The type of isomerism shown by the complex [CoCl₂(en)₂] is
a.
Ionization isomerism
b.
Coordination isomerism
c.
Geometrical isomerism
d.
Linkage isomerism
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Q161 mcq
The geometry and magnetic behaviour of the complex [Ni(CO)₄] are
a.
Square planar geometry and paramagnetic
b.
Tetrahedral geometry and diamagnetic
c.
Square planar geometry and diamagnetic
d.
Tetrahedral geometry and paramagnetic
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Q162 mcq
Iron carbonyl, Fe(CO)₅ is
a.
Trinuclear
b.
Mononuclear
c.
Tetranuclear
d.
Dinuclear
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Q163 mcq
The correct difference between first- and second-order reactions is that
a.
A first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed
b.
The half-life of a first-order reaction does not depend on [A]₀; the half-life of a second-order reaction does depend on [A]₀
c.
The rate of a first-order reaction does not depend on reactant concentrations; the rate of a second-order reaction does depend on reactant concentrations
d.
The rate of a first-order reaction does depend on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations
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Q164 mcq
Among CaH₂, BeH₂, BaH₂, the order of ionic character is
a.
BeH₂ < BaH₂ < CaH₂
b.
CaH₂ < BeH₂ < BaH₂
c.
BeH₂ < CaH₂ < BaH₂
d.
BaH₂ < BeH₂ < CaH₂
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Q166 mcq
In which case is the number of molecules of water maximum?
a.
0.00224 L of water vapours at 1 atm and 273 K
b.
0.18 g of water
c.
18 mL of water
d.
10⁻³ mol of water
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Q167 mcq
Which of the following molecules represents the order of hybridisation sp², sp², sp, sp from left to right atoms?
a.
CH₂=CH–CH=CH₂
b.
CH₂=CH–C≡CH
c.
HC≡C–C≡CH
d.
CH₃–CH=CH–CH₃
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Q169 mcq
Which of the following is correct with respect to –I effect of the substituents? (R = alkyl)
a.
–NH₂ > –OR > –F
b.
–NR₂ < –OR < –F
c.
–NH₂ < –OR < –F
d.
–NR₂ > –OR > –F
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Q171 mcq
Which of the following compounds can form a zwitterion?
a.
Benzoic acid
b.
Acetanilide
c.
Aniline
d.
Glycine
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Q172 mcq
The compound A on treatment with Na gives B, and with PCl₅ gives C. B and C react together to give diethyl ether. A, B and C are in the order
a.
C₂H₅Cl, C₂H₆, C₂H₅OH
b.
C₂H₅OH, C₂H₅Cl, C₂H₅ONa
c.
C₂H₅OH, C₂H₆, C₂H₅Cl
d.
C₂H₅OH, C₂H₅ONa, C₂H₅Cl
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Q173 mcq
Hydrocarbon (A) reacts with bromine by substitution to form an alkyl bromide which by Wurtz reaction is converted to gaseous hydrocarbon containing less than four carbon atoms. (A) is
a.
CH₃–CH₃
b.
CH₂=CH₂
c.
CH≡CH
d.
CH₄
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Q175 mcq
Which oxide of nitrogen is not a common pollutant introduced into the atmosphere both due to natural and human activity?
a.
N₂O
b.
NO₂
c.
N₂O₅
d.
NO
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Q175 mcq
Which oxide of nitrogen is not a common pollutant introduced into the atmosphere both due to natural and human activity?
a.
N₂O
b.
NO₂
c.
N₂O₅
d.
NO
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Q176 mcq
Regarding cross-linked or network polymers, which of the following statements is incorrect?
a.
Examples are bakelite and melamine.
b.
They are formed from bi- and tri-functional monomers.
c.
They contain covalent bonds between various linear polymer chains.
d.
They contain strong covalent bonds in their polymer chains.
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Q176 mcq
Regarding cross-linked or network polymers, which of the following statements is incorrect?
a.
Examples are bakelite and melamine.
b.
They are formed from bi- and tri-functional monomers.
c.
They contain covalent bonds between various linear polymer chains.
d.
They contain strong covalent bonds in their polymer chains.
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Q177 mcq
Which of the following oxides is most acidic in nature?
a.
BaO
b.
BeO
c.
MgO
d.
CaO
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Q177 mcq
Which of the following oxides is most acidic in nature?
a.
BaO
b.
BeO
c.
MgO
d.
CaO
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Q178 mcq
Nitration of aniline in strong acidic medium also gives m-nitroaniline because
a.
In absence of substituents nitro group always goes to m-position.
b.
In electrophilic substitution reactions amino group is meta directive.
c.
In spite of substituents nitro group always goes to only m-position.
d.
In acidic (strong) medium aniline is present as anilinium ion.
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Q179 mcq
A mixture of 2.3 g formic acid and 4.5 g oxalic acid is treated with conc. H₂SO₄. The evolved gaseous mixture is passed through KOH pellets. Weight (in g) of the remaining product at STP will be
a.
2.8
b.
3.0
c.
1.4
d.
4.4
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Q180 mcq
The difference between amylose and amylopectin is
a.
Amylopectin has α(1→4) linkage and α(1→6) linkage.
b.
Amylose has α(1→4) linkage and α(1→6) linkage.
c.
Amylopectin has α(1→4) linkage and α(1→6) linkage.
d.
Amylose is made up of glucose and galactose.
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