datavorous/entrance-exam-dataset huggingface dataset:
Which one of the following sets correctly represents the increase in the paramagnetic property of the ions?

Options:
A $\mathrm{Cu}^{2+}>\mathrm{V}^{2+}>\mathrm{Cr}^{2+}>\mathrm{Mn}^{2+}$
B $\mathrm{Cu}^{2+} < \mathrm{Cr}^{2+} < \mathrm{V}^{2+} < \mathrm{Mn}^{2+}$
C $\mathrm{Cu}^{2+} < \mathrm{V}^{2+} < \mathrm{Cr}^{2+} < \mathrm{Mn}^{2+}$
D $\mathrm{V}^{2+} < \mathrm{Cu}^{2+} < \mathrm{Cr}^{2+} < \mathrm{Mn}^{2+}$

The correct answer is:
$\mathrm{Cu}^{2+} < \mathrm{V}^{2+} < \mathrm{Cr}^{2+} < \mathrm{Mn}^{2+}$

Solution:
Paramagnetic nature depends upon the number of unpaired electrons. Higher the number of unpaired electrons, higher the paramagnetic property will be.
$\mathrm{Cu}^{2+}=[\mathrm{Ar}] 3 d^{9}$, no. of unpairedelectrons $=1$
$\mathrm{V}^{2+}=[\mathrm{Ar}] 3 d^{3}$, no. ofunpaired electrons $=3$
$\mathrm{Cr}^{2+}=[\mathrm{Ar}] 3 d^{4}$, no. of unpaired electrons $=4$
$\mathrm{Mn}^{2+}=[\mathrm{Ar}] 3 Å^{5}$, no. of unpairedelectrons $=5$
Hence, correct order is
$$
\mathrm{Cu}^{2+} < \mathrm{V}^{2+} < \mathrm{Cr}^{2+} < \mathrm{Mn}^{2+}
$$

Topic: Chemistry, d and f Block Elements, JEE Main
Which one of the following sets forms the biodegradable polymer?

Options:
A $\mathrm{CH}_2=\mathrm{CH}-\mathrm{CN}$ and $\mathrm{CH}_2=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_2$
B $\mathrm{H}_2 \mathrm{~N}-\mathrm{CH}_2-\mathrm{COOH}$ and $\mathrm{H}_2 \mathrm{~N}-\left(\mathrm{CH}_2\right)_5-\mathrm{COOH}$
C $\mathrm{HO}-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{OH}$ and

D

The correct answer is:
$\mathrm{H}_2 \mathrm{~N}-\mathrm{CH}_2-\mathrm{COOH}$ and $\mathrm{H}_2 \mathrm{~N}-\left(\mathrm{CH}_2\right)_5-\mathrm{COOH}$

Solution:
Biodegradable polymers have tendency to break down and lose their initial integrity.
$$
\begin{aligned}
& \mathrm{H}_2 \mathrm{~N}-\mathrm{CH}_2-\mathrm{COOH}+\mathrm{HNH}\left(\mathrm{CH}_2\right)_5 \mathrm{COOH} \\
& \Delta \downarrow-\mathrm{H}_2 \mathrm{O} \\
& {\left[\mathrm{HN}-\mathrm{CH}_2-\mathrm{CO}-\mathrm{NH}-\left(\mathrm{CH}_2\right)_5-\mathrm{CO}_n\right.} \\
&
\end{aligned}
$$
Nylon-2-nylon-6

Topic: Chemistry, Polymers, NEET, NEET 2012 (Mains)
Which one of the following sets of ions represents a collection of isoelectronic species?

(Given : Atomic Number : F:9,Cl:17,Na=11

Mg=12,Al=13, K=19,Ca=20,Sc=21)

Options:
A Li+,Na+,Mg2+,Ca2+
B Ba2+,Sr2+,K+,Ca2+
C N3-,O2-,F-,S2-
D K+,Cl-,Ca2+,Sc3+

The correct answer is:
K+,Cl-,Ca2+,Sc3+

Solution:
Isoelectronic species have same no. of electrons. Below are the isoelectronic species with their respective no. of electrons:
K+ Cl- Ca2+Sc3+18181818
All of the above elements have the electronic configuration of argon.

Topic: Chemistry, Structure of Atom, JEE Main, JEE Main 2023 (01 Feb Shift 2)
Which one of the following sets of ions represents a collection of isoelectronic species?

Options:
A
$\mathrm{K}^{+}, \mathrm{Cl}^{-}, \mathrm{Ca}^{2+}, \mathrm{Sc}^{3+}$

B
$\mathrm{Ba}^{2+}, \mathrm{Sr}^{2+}, \mathrm{K}^{+}, \mathrm{S}^{2-}$

C
$\mathrm{N}^{3-}, \mathrm{O}^{2-}, \mathrm{F}^{-}, \mathrm{S}^{2-}$

D
$\mathrm{Li}^{+}, \mathrm{Na}^{+}, \mathrm{Mg}^{2+}, \mathrm{Ca}^{2+}$

The correct answer is:
$\mathrm{K}^{+}, \mathrm{Cl}^{-}, \mathrm{Ca}^{2+}, \mathrm{Sc}^{3+}$

Solution:
No Solution Available

Topic: Chemistry, Structure of Atom, JEE Main, JEE Main 2006
Which one of the following sets of ions represents the collection of isoelectronic species?

Options:
A $\mathrm{K}^{+}, \mathrm{Cl}^{-}, \mathrm{Mg}^{2+}, \mathrm{Sc}^{3+}$
B $\mathrm{Na}^{+}, \mathrm{Ca}^{2+}, \mathrm{Sc}^{3+}, \mathrm{F}^{-}$
C $\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Sc}^{3+}, \mathrm{Cl}^{-}$
D $\mathrm{Na}^{+}, \mathrm{Mg}^{2+}, \mathrm{Al}^{3+}, \mathrm{Cl}^{-}$

The correct answer is:
$\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Sc}^{3+}, \mathrm{Cl}^{-}$

Solution:
The number of electrons in these species are
$\therefore \mathrm{Na}^{+}, \mathrm{Mg}^{2+}, \mathrm{Al}^{3+}$ and $\mathrm{F}^{-}$are isoelectronic species and each one of which has 10. Also, $\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{SC}^{3+}$ and $\mathrm{Cl}^{-}$are electronic species and each one of which has 18 electrons.

Topic: Chemistry, Structure of Atom, JEE Main
Which one of the following sets of items in the options 1-4 are correctly categorised with one exception in it?

Options:
A (a)
B (b)
C (c)
D (d)

The correct answer is:
(c)

Solution:
Plasmodium and Trypanosoma are protozoan parasite while Cuscuta is angiospermic parasite. Typhoid, pneumonia and diphtheria are caused by bacteria.

Topic: Biology, Molecular Basis of Inheritance, NEET, NEET 2012 (Mains)
Which one of the following shows optical activity

Options:
A

B

C

D

The correct answer is:

Solution:

Topic: Chemistry, General Organic Chemistry, JEE Main
Which one of the following species doesn't have a magnetic moment of 1.73BM, (spin only value)?

Options:
A O2+
B CuI
C CuNH34Cl2
D O2-

The correct answer is:
CuI

Solution:
Species must not contain single unpaired

O2+→σ1 s2<σ1 s*2<σ2 s2<σ2 s*2<σ2pz2<π2px2=π2py2<π2px*1=π2py*0

unpaired e-=1∴μ=1.73 BM

(1) Cu+I-Cu+→[Ar]3 d10∴ unpaired e-=0

I-→[Xe]∴ unpaired e-=0

therefore μ=0

3. CuNH34Cl2

Cu→[A]3 d3∴ unpaired =1∴μ=1.73 BM

4. O2-→d

σ1 s2<σ1 s*2<σ2 s2<σ2 s*2<σ2pz2<π2px2=π2py2<π2px*2=π2py*1

1 Unpaired electron

∴ unpaired ∴μ=1.73 BM

Topic: Chemistry, Structure of Atom, JEE Main, JEE Main 2021 (20 Jul Shift 2)
Which one of the following species is diamagnetic in nature

Options:
A $\mathrm{He}_2^{+}$
B $\mathrm{H}_2$
C $\mathrm{H}_2^{+}$
D $\mathrm{H}_2^{-}$

The correct answer is:
$\mathrm{H}_2$

Solution:
( $P=$ Paramagnetic, $D=$ Diamagnetic $)$

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main
Which one of the following species is diamagnetic in nature?

Options:
A
$\mathrm{He}_2^{+}$

B
$\mathrm{H}_2$

C
$\mathrm{H}_2^{+}$

D
$\mathrm{H}_2^{-}$

The correct answer is:
$\mathrm{H}_2$

Solution:
$\mathrm{H}_2 \sigma 1 \mathrm{~s}^2 \sigma^* 1 \mathrm{~s}^0$, no unpaired so diamagnetic

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main, JEE Main 2005
Which one of the following species is stable in aqueous solution?

Options:
A Cr2+
B MnO42-
C MnO43-
D Cu+

The correct answer is:
MnO42-

Solution:
In MnO42-, manganese is in +6 oxidation state, which is having the highest stability.
MnO4-2⇒​x+4 -2=-2
x=6
Cu+⇒x=+1 It will disproportionate in aqueous solution.
Cr+2⇒x=+2 It will also disproportionate in aqueous solution.
MnO4-3⇒x+4-2=-3 Mn is not stable in +5 oxidation state.
x=5
Higher the oxidation state, more is the stability of the species.

Topic: Chemistry, d and f Block Elements, JEE Main
Which one of the following species is stable in aqueous solution?

Options:
A Cr2+
B MnO42-
C MnO43-
D Cu+

The correct answer is:
MnO42-

Solution:
In MnO42-, manganese is in +6 oxidation state, which is having the highest stability.
MnO4-2⇒​x+4 -2=-2
x=6
Cu+⇒x=+1 It will disproportionate in aqueous solution.
Cr+2⇒x=+2 It will also disproportionate in aqueous solution.
MnO4-3⇒x+4-2=-3 Mn is not stable in +5 oxidation state.
x=5
Higher the oxidation state, more is the stability of the species.

Topic: Chemistry, d and f Block Elements, JEE Main, JEE Main 2016 (09 Apr Online)
Which one of the following species responds to an external magnetic field?

Options:
A FeH2O63+
B NiCN42-
C CoCN63-
D NiCO4

The correct answer is:
FeH2O63+

Solution:
1. FeH2O63+

Fe3+ : Ar3d5

Hybridisation : sp3d2

Magnetic nature : Paramagnetic (so this complex response to external magnetic field)

2. NiCN42-

Ni3+ : Ar3d8

Hybridisation : dsp2

Magnetic nature : diamagnetic

3. CoCN63-

Co3+ : Ar3d6

Hybridisation : d2sp3

Magnetic nature : diamagnetic

4. NiCO4

Ni : Ar3d8 4s2

Hybridisation : sp3

Magnetic nature : diamagnetic

Topic: Chemistry, Coordination Compounds, JEE Main, JEE Main 2021 (25 Jul Shift 1)
Which one of the following spherical lenses do not exhibit dispersion? The radii of curvatures of the surfaces of the lenses are as given in the diagrams.

Options:
A
B
C
D

The correct answer is:

Solution:
1f=Î¼-11R1-1R2
For no dispersion d1f=0
dÎ¼-11R1-1R2=0 âR1=R2

Topic: Physics, Ray Optics, JEE Main
Which one of the following statement is correct?

Options:
A $\mathrm{e}^{\mathrm{x}}$ is an increasing function $\quad$
B $\mathrm{e}^{\mathrm{x}}$ is a decreasing function
C $\mathrm{e}^{\mathrm{x}}$ is neither increasing nor decreasing function
D $\mathrm{e}^{\mathrm{x}}$ is a constant function

The correct answer is:
$\mathrm{e}^{\mathrm{x}}$ is an increasing function $\quad$

Solution:
From the graph of $\mathrm{e}^{x}$ it is clear that $\mathrm{e}^{\mathrm{x}}$ is an increasing function. Also Domain $=\mathrm{R}$ and Range $=\mathrm{R}^{+}$

Topic: Mathematics, Application of Derivatives, NDA, NDA 2012 (Phase 1)
Which one of the following statement is correct ?

Options:
A Malignant tumours may exhibit metastasis
B Patients who have undergone surgery are given cannabinoids to relieve pain.
C Benign tumours show the property of metastasis
D Heroin accelerates body functions.

The correct answer is:
Malignant tumours may exhibit metastasis

Solution:
No Solution Available

Topic: Biology, Human Health and Diseases, NEET, NEET 2009 (Mains)
Which one of the following statement is incorrect about menstruation?

Options:
A During normal menstruation about $40 \mathrm{~mL}$ blood is lost
B The menstrual fluid can easily clot
C At menopause in the female, there is especially abrupt increase in gonadotropic hormones
D The beginning of the cycle of menstruation is called menarche

The correct answer is:
The menstrual fluid can easily clot

Solution:
During normal menstruation approximately $40 \mathrm{~mL}$ of blood and an additional $35 \mathrm{~mL}$ of serous fluid are lost. The menstrual fluid is normally non-clotting because a fibrinolysin is released alongwith necrotic endometrial material.
The cause of menopause is burning out of the ovaries. At about age 45 years only a few primordial follicles remain to be stimulated by FSH and LH. The estrogen production fall below a critical value and the gonadotropic hormones (FSH and $\mathrm{LH}$ ) are produced regularly from the pituitary so, there level increase in body.

Topic: Biology, Human Reproduction, NEET, NEET 2008 (Screening)
Which one of the following statement is not correct for most common type of nephrons of human kidney?

Options:
A They are small size, less coiled with major part present at the junction of cortex and medulla.
B They have short length of loop of Henle.
C They do not have major role to form Counter current mechanism.
D They have no or highly reduced Vasa recta.

The correct answer is:
They are small size, less coiled with major part present at the junction of cortex and medulla.

Solution:
The human kidney has about 85% cortical nephrons and about 15% juxta-medullary nephrons. The cortical nephrons are highly coiled structures with major parts present in the cortex region. Juxta-medullary nephrons have a long loop of Henle which runs deep in the medulla, well developed Vasa recta, and are mainly activated during a shortage of water.

Topic: Biology, Excretory Products and their Elimination, NEET
Which one of the following statement is not true?

Options:
A Lactose contains α-glycosidic linkage between C1 of galactose and C4 of glucose
B Lactose is a reducing sugar and it gives Fehling's test.
C Lactose C11H22O11 is a disaccharide and it contains 8 hydroxyl groups.
D On acid hydrolysis, lactose gives one molecule of D+-glucose and one molecule of D+-galactose.

The correct answer is:
Lactose contains α-glycosidic linkage between C1 of galactose and C4 of glucose

Solution:
The linkage is between C-1 of Galactose and C-4 of Glucose

Lactose (Milk sugar) →H3O⊕β-galactose + β-glucose

C12H22O11

it is hydrolysed by dilute acids or by the enzyme lactase, to an equimolecular mixture of D+-glucose and D+-galactose. Lactose is a reducing sugar.

Topic: Chemistry, Biomolecules, JEE Main, JEE Main 2020 (06 Sep Shift 2)
Which one of the following statement is totally wrong about the occurrence of notochord, while the other three are correct?

Options:
A It is present only in larval tail in Ascidians
B It is replaced by a vertebral column in adult frog
C It is absent throughout life in humans from the very beginning
D It is present throughout life in Amphioxus

The correct answer is:
It is absent throughout life in humans from the very beginning

Solution:
The notochord is a flexible rod-like structure that forms the main support of the body in the lowest chordates. It is not absent in humans throughout their life. The notochord is present in the embryonic stage and gets changed or replaced by the vertebral column in the adult.

Topic: Biology, Animal Kingdom, NEET
Which one of the following statement is true regarding digestion and absorption of food in humans?

Options:
A Oxyntic cells in our stomach secrete the proenzyme pepsinogen.
B Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like K+.
C Chylomicrons are small lipoprotein particles that are transported from the intestine into lacteals.
D About 60% of starch is hydrolysed by salivary amylase in our mouth.

The correct answer is:
Chylomicrons are small lipoprotein particles that are transported from the intestine into lacteals.

Solution:
Chylomicrons are lipoprotein particles synthesized by intestinal epithelial cells and consisting mainly of triglycerides. Chylomicrons are the form, in which dietary fat is transported in the circulatory system.

Topic: Biology, Digestion and Absorption, NEET
Which one of the following statement is true regarding digestion and absorption of food in humans :

Options:
A About $60 \%$ of starch is hydrolysed by salivary amylase in our mouth
B Oxyntic cells in our stomach secrete the proenzyme pepsinogen
C Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $\mathrm{Na}^{+}$
D Chylomicrons are small lipoprotein particles that are transported from intestine into blood capillaries

The correct answer is:
Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $\mathrm{Na}^{+}$

Solution:
No Solution Available

Topic: Biology, Digestion and Absorption, NEET, NEET 2009 (Mains)
Which one of the following statement is true regarding digestion and absorption of food in humans?

Options:
A Oxyntic cells in our stomach secrete the proenzyme pepsinogen.
B Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $\mathbf{N a}^{+}$.
C Chylomicrons are small lipoprotein particles that are transported from intestine into blood capillaries.
D About $60 \%$ of starch is hydrolysed by salivary amylase in our mouth.

The correct answer is:
Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $\mathbf{N a}^{+}$.

Solution:
Chylomicrons are lipoprotein particles synthesized by intestinal epithelial cells and consisting mainly of triglycerides. Chylomicrons are the form, in which dietory fat is transported in the circulatory system.

Topic: Biology, Digestion and Absorption, NEET, NEET 2009 (Screening)
Which one of the following statement is true regarding digestion and absorption of food in humans?

Options:
A Chief cells in our stomach secrete HCl.
B Fructose and amino acids are absorbed through the inner lining of stomach with the help of carrier ions like Ca+2.
C Chylomicrons are small lipoprotein particles that are transported from the intestine into blood capillaries.
D About 60% of starch is hydrolyzed in the stomach.

The correct answer is:
Chylomicrons are small lipoprotein particles that are transported from the intestine into blood capillaries.

Solution:
Chylomicrons are lipoprotein particles synthesized by intestinal epithelial cells and consisting mainly of triglycerides. Chylomicrons are the form, in which dietary fat is transported in the circulatory system.

Topic: Biology, Digestion and Absorption, NEET
Which one of the following statements about all the four of Spongilla, leech, dolphin and penguin is correct?

Options:
A Penguin is homoiothermic while the remaining three are poikilothermic
B Leech is a fresh water form while all others are marine
C Spongilla has special collared cells called choanocytes, not found in the remaining three
D All are bilaterally symmetrical

The correct answer is:
Spongilla has special collared cells called choanocytes, not found in the remaining three

Solution:
Spongilla belongs to phylum-Porifera, in which, choanoytes are the characteristic cells, these are absent in leech, dolphin and pengiun. These distinctive cells line the interior body walls of sponges. These cells have a central flagellum that is surrounded by a collar of micovilli. Choanocytes are versatile cells. Their flagella beat to create the active pumping of water through the sponge, while the collars of the choanocytes are the primary areas where nutrients are absorbed into the sponge.

Topic: Biology, Animal Kingdom, NEET, NEET 2010 (Screening)
Which one of the following statements about all the four of Spongilla, Leech, Dolphin and Penguin is CORRECT?

Options:
A Penguin is homoeothermic while the remaining three are poikilothermic.
B Leech is a freshwater form while all others are marine.
C Spongilla has special collared cells called choanocytes, not found in the remaining three.
D All of them shows bilateral symmetry.

The correct answer is:
Spongilla has special collared cells called choanocytes, not found in the remaining three.

Solution:
Penguin is a flightless bird belonging to the group of Aves and is a homeotherm. Dolphin is an aquatic mammal that gives birth to live young ones and found in both freshwater and marine water. It is also homeotherm.
Leech is a segmented parasite under the phylum Annelida majorly found in the freshwater habitat. They are hermaphrodites and poikilothermic.
Spongilla is a freshwater sponge found in lakes in slow streams. They remain attached to the rock and logs surface and filter water using their special cells called choanocytes. It obtains it nutrient through this process.
The symmetry of leech, penguin and dolphin is bilateral and that is Spongilla is asymmetrical.

Topic: Biology, Animal Kingdom, NEET
Which one of the following statements about erythrocytes is false?

Options:
A In the life cycle of a foetus, erythropoiesis takes place in both liver and bone marrow.
B They maintain the viscosity of blood.
C They maintain blood pH as they contain haemoglobin which acts as a buffer.
D The total quantity of RBCs in a human male body is around 5.5 million.

The correct answer is:
The total quantity of RBCs in a human male body is around 5.5 million.

Solution:
The erythrocytes or RBCs are cells of blood produced by the red bone marrow in adults and by the liver in the foetal stage. The liver also helps in destroying old and worn out RBCs. These cells contain the respiratory pigment haemglobin which acts as a buffer as it can bind to small amounts of acid in the blood, helping to remove that acid before it fluctuates the pH of blood. These RBCs also tend to aggregate thereby increasing the viscosity of blood.
However the quantity of RBCs in blood is approximately 5.5 million per cubic mm of blood i.e. in one tiny droplet of blood.

Topic: Biology, Body Fluids and Circulation, NEET
Which one of the following statements about packing in solids is incorrect ?

Options:
A
Coordination number in bcc mode of packing is 8 .

B
Coordination number in hep mode of packing is 12 .

C
Void space in hcp mode of packing is $32 \%$.

D
Void space in ccp mode of packing is $26 \%$.

The correct answer is:
Void space in hcp mode of packing is $32 \%$.

Solution:
The $h c p$ arrangement of atoms occupies $74 \%$ of the available space and thus has $26 \%$ vacant space.

Topic: Chemistry, Solid State, JEE Main, JEE Main 2013 (22 Apr Online)
Which one of the following statements about the particular entity is true?

Options:
A Centromere is found in animal cells which produces aster during cell division
B The gene for producing insulin is present in every body cell
C Nucleosome is formed of nucleotides
D DNA consists of a core of eight histones

The correct answer is:
The gene for producing insulin is present in every body cell

Solution:
Scientists have analysed the human DNA sequence present in a human-mouse somatic cell hybrid line possessing a translocation involving human chromosome-II and $\mathrm{X}$. This data indicates that the human insulin gene is located on the short arm of chromosome-II in every body cell but is not expressed in all cells.

Topic: Biology, Cell Cycle and Cell Division, NEET, NEET 2010 (Mains)
Which one of the following statements about the zeolites is false

Options:
A Zeolites are aluminosilicates having three dimensional network
B Some of $\mathrm{SiO}_4^{-4}$ the units are replaced by $\mathrm{AlO}_4^{-5}$ and $\mathrm{AlO}_6^{9-}$ ions in zeolites
C They are used as cation exchangers
D They have open structure which enables them to take up small molecules

The correct answer is:
Some of $\mathrm{SiO}_4^{-4}$ the units are replaced by $\mathrm{AlO}_4^{-5}$ and $\mathrm{AlO}_6^{9-}$ ions in zeolites

Solution:
Zeolite have $\mathrm{SiO}_4^{-4}$ and $\mathrm{AlO}_4^{-5}$ tetrahedrons linked together in a three dimensional open structure in which four or six membered ring predominate. Due to open chain structure they have cavities and can take up water and other small molecules

Topic: Chemistry, p Block Elements (Group 13 & 14), JEE Main
Which one of the following statements about water is false?

Options:
A Ice formed by heavy water sinks in normal water
B Water oxidized to oxygen during photosynthesis
C Water can act both as an acid and as a base
D There is extensive intramolecular hydrogen bonding in the condensed phase

The correct answer is:
There is extensive intramolecular hydrogen bonding in the condensed phase

Solution:
(i) Ice formed by heavy water sinks in normal water due to higher density of D2O than normal water
(ii) 6CO2+6H2O→hvchlorophyllC6H12O6+6O2
(iii) Water can show amphiprotic nature and hence water can act both as an acid a base
(iv) There is extensive intermolecular hydrogen bonding in the condensed phase instead of intramolecular H-bonding

Topic: Chemistry, s Block Elements, JEE Main
Which one of the following statements are true?
(1) Transition metals form alloys
(2) Transition metals form complexes
(3) Zn, Cd and Hg are transition metals
(4) K2PtCl6 is a well known compound, but corresponding nickel compound is not known.

Options:
A 1, 2
B 2, 4
C 1, 2, 4
D 2, 3, 4

The correct answer is:
1, 2, 4

Solution:
Here statement (3) is not true as Zn, Cd and Hg are not regarded transition metals, because the neutral atoms as well as stable ions have fully-filled d-orbitals.
Statements (1), (2) and (4) are true as transition metals have similar atomic sized, therefore, in the crystal lattice, one transition metals atoms can be easily replaced by the atoms of another transition metal to form alloy. They can easily form complexes, because they form small highly charged cations, which have vacant orbitals of suitable energy to accept electron pairs donated by ligands.
As the sum of first four ionization energies of Pt is less than the sum of first four ionization energies of Ni, so K2PtCl6 is more stable than the corresponding nickel compound.

Topic: Chemistry, d and f Block Elements, JEE Main
Which one of the following statements can best explain the term critical concentration of an essential element?

Options:
A
essential element concentration below which plant growth is retarded

B
essential element concentration below which plant growth becomes enhanced

C
essential element concentration below which plant remains in the vegetative phase

D
None of the above

The correct answer is:
essential element concentration below which plant growth is retarded

Solution:
The concentration of an essential element below which the plant growth is retarded is known as critical concentration. Plants start displaying deficiency symptoms if a particular element is present below the critical concentration.

Topic: Biology, Mineral Nutrition