datavorous/entrance-exam-dataset huggingface dataset:
Which molecules has zero dipole moment

Options:
A $\mathrm{H}_2 \mathrm{O}$
B $\mathrm{CO}_2$
C $\mathrm{HF}$
D $\mathrm{HBr}$

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

Solution:
$\mathrm{CO}_2$ is a symmetrical molecule so its dipole moment is zero

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main
Which number should be added to the numbers $13,15,19$ so that the resulting numbers be the consecutive terms of a H.P.

Options:
A $7$
B $6$
C $-6$
D $-7$

The correct answer is:
$-7$

Solution:
Suppose that $X$ to be added then numbers $13,15,19$ so that new numbers $x+13,15+x, 19+x$ will be in H.P.
$\Rightarrow \quad(15+x)=$$\frac{2(x+13)(19+x)}{x+13+x+19}$
$\Rightarrow x^2+31 x+240=x^2+32 x+247 \Rightarrow x=-7$
Trick : Such type of questions should be checked with the options.

Topic: Mathematics, Sequences and Series, JEE Main
Which of following is a pair of viral diseases?

Options:
A Typhoid, Tuberculosis
B Ringworm, AIDS
C Common Cold, AIDS
D Dysentery, Common Cold

The correct answer is:
Common Cold, AIDS

Solution:
No Solution Available

Topic: Biology, Human Health and Diseases, NEET, NEET 2009 (Mains)
Which of following reagents does not give isobutane when reacted with isobutyl magnesium bromide?

Options:
A CH3–C≡CH
B
C CH3–CH2–OH
D PhOCH3

The correct answer is:
PhOCH3

Solution:
As Ph–O–CH3 don't have acidic H so it can not take part in acid base reaction.

Topic: Chemistry, Hydrocarbons, JEE Main
Which of the acids cannot be prepared by grignard reagent

Options:
A Acetic acid
B Succinic acid
C Formic acid
D All of these

The correct answer is:
Formic acid

Solution:

Topic: Chemistry, Carboxylic Acid Derivatives, JEE Main
Which of the alkaline earth metal halides given below is essentially covalent in nature?

Options:
A BeCl2
B MgCl2
C SrCl2
D CaCl2

The correct answer is:
BeCl2

Solution:
Be2+ cation is very small in size and in terms of Fajan's rules brings about polarization of electronic cloud of anion (Cl-) i.e. BeCl2 is covalent in nature.

Topic: Chemistry, s Block Elements, JEE Main, JEE Main 2015 (11 Apr Online)
Which of the below mentioned regions exhibit less seasonal variations?

Options:
A
Tropics

B
Temperates

C
Alpines

D
Both (a) and (b)

The correct answer is:
Tropics

Solution:
The tropical region exhibit less seasonal variations, i.e., it remain undisturbed.
The temperate region are more seasonal, less constant and exhibit less species diversity. Alpines also, show less diversity with low temperature and high altitudes.

Topic: Biology, Biodiversity and its Conservation
Which of the $C-C$ bond is strongest

Options:
A Formed by $s p^3-s p^3$ hybridised carbon atoms (as in alkanes)
B Formed by $s p^2-s p^2$ hybridised carbon atoms (as in alkenes)
C Formed by $s p-s p$ hybridised carbon atoms (as in alkynes)
D All are equal

The correct answer is:
Formed by $s p-s p$ hybridised carbon atoms (as in alkynes)

Solution:
$s p-s p\gts p^2-s p^2\gts p^3-s p^3$

Topic: Chemistry, Hydrocarbons, JEE Main
Which of the cells stay in the Go phase?

Options:
A Multinucleated muscle cells
B Heart muscle cells
C Neurons
D All of these

The correct answer is:
All of these

Solution:
Cell cycle is divided into two phases - Interphase and Mitosis (M) phase. The interphase is further divide into 3 phases - Gap/G o phase, G1 phase, Synthesis (S) phase and G2 phase. Certain types of cells in the body divide occasionally when there is a need. These type of cells do not proceed further in the cell cycle and exit the G1 phase to enter into a stage of inactivity known as the quiescent stage or Go phase. In this stage the cells remain metabolically active but do not proliferate unless and until there is need. Multinucleated muscle cells, heart muscle cells and neuronswhich doesn't undergo cytokinesis and are considered to be in the G0 stage, which will never enter the G1 phase.

Topic: Biology, Cell Cycle and Cell Division, NEET
Which of the characteristics is not common between [Cu(en)2]2+ and [Ni(dmg)2] ?

Options:
A Geometry of complexes
B Hybridisation of central metal cation
C Magnetic behaviour
D Number of stereoisomers

The correct answer is:
Magnetic behaviour

Solution:
Geometry of complexes → Both square planar
Hybridisation of central metal cation →dsp2
Magnetic behaviour [Cu(en)2]2+→ Paramagnetic; [Ni(dmg)2]→ Diamagentic
Number of stereoisomers = 0.

Topic: Chemistry, Coordination Compounds, JEE Main
Which of the complexes is expected to have lowest Δ 0 value? [consider only magnitude]

Options:
A Co NH 3 6 3+
B Rh NH 3 6 3+
C Ir NH 3 6 3+
D CoF 6 3−

The correct answer is:
CoF 6 3−

Solution:
The magnitude of Δ 0 varies from stronger to weaker ligand. According to spectrochemical series, F − is a weaker ligand while NH 3 is a stronger ligand. Stronger ligand gives a larger value of Δ 0 .
Hence, among the given complexes CoF 6 3− is expected to have lowest value of Δ 0 value.

Topic: Chemistry, Coordination Compounds, JEE Main
Which of the compounds exist mainly in the enol form?

Options:
A
B
C
D All of these

The correct answer is:
All of these

Solution:
All these are stable in enol forms as follows

Topic: Chemistry, Alcohols Phenols and Ethers, NEET
Which of the diode circuit shows correct biasing used for the measurement of dynamic resistance of p-n junction diode :

Options:
A
B
C
D

The correct answer is:

Solution:
Diode should be in forward biased to calculate dynamic resistance.

Topic: Physics, Semiconductors, JEE Main, JEE Main 2024 (04 Apr Shift 2)
Which of the following 0.1 M aqueous solution will have lowest freezing point?

Options:
A Potassium sulphate
B Sodium chloride
C Urea
D Glucose

The correct answer is:
Potassium sulphate

Solution:
Potassium sulphate K2SO4, i=3

Sodium chloride NaCl, i=2

Urea, i=1

Glucose, i=1

Greater the value of i, greater lowering in freezing point and hence, lower will be the freezing temperature.

Therefore, K2SO4 solution has the lowest freezing point.

Topic: Chemistry, Solutions, JEE Main
Which of the following 3d-metal ion will give the lowest enthalpy of hydration ΔhydH when dissolved in water?

Options:
A Cr2+
B Mn2+
C Fe2+
D Co2+

The correct answer is:
Mn2+

Solution:
Hydration enthalpy (êHHyd) is the change in enthalpy when one mole of gaseous ion under a standard condition of 1 bar pressure dissolves in a sufficient amount of water to form an infinitely dilute solution (infinite dilution means a further addition of solute will not cause any heat change).

Hydration enthalpy is inversely related to the size of the ion, smaller the size of the ion greater is the hydration and hence greater is the hydration energy released.

Mn+2 has the lowest hydration energy among the given ions as it has the largest size.

Ion	ΔHHyd.o(kJ/mole)

Cr2+	-1925

Mn2+	-1862

Fe2+	-1998

Co2+	-2079

Topic: Chemistry, d and f Block Elements, JEE Main, JEE Main 2022 (29 Jul Shift 2)
Which of the following acid will form an
(a) Anhydride on heating and
(b) Acid imide on strong heating with ammonia?

Options:
A
B
C
D

The correct answer is:

Solution:

Topic: Chemistry, Carboxylic Acid Derivatives, JEE Main
Which of the following acids does not contain
-COOH group?

Options:
A Carbamic acid
B Barbituric acid
C Lactic acid
D Succinic acid

The correct answer is:
Barbituric acid

Solution:
Carbamic acid $\quad \mathrm{HOOC}-\mathrm{NH}_{2}$
(b) Barbituric acid $\quad \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{~N}_{2} \mathrm{O}_{3}$
(c) Lactic acid
(d) Succinic acid HOOC $-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}$
Therefore, barbituric acid is actually not an acid.

Topic: Chemistry, Carboxylic Acid Derivatives, JEE Main
Which of the following acids, does NOT undergo Hell-Vohlard-Zelinsky reaction?

Options:
A Butanoic acid
B Propanoic acid
C Ethanoic acid
D Methanoic acid

The correct answer is:
Methanoic acid

Solution:
Carboxylic acid which contain a – hydrogen atom reacts with chlorine or bromine in presence of red phosphorus to give a – chloro or a – bromo acids. This reaction is called H.V.Z (Hell Volhard Zelinsky ) reaction. CH3COOH ? CCl3COOH(trichloroacetic acid). CH3CH2COOH ? CH3CBr2COOH (a,a-dibromopropionic acid) Due to absence of a – H atom HCOOH does not undergo HVZ reaction.

Topic: Chemistry, Carboxylic Acid Derivatives, JEE Main
Which of the following act as a supporting framework for epithelium?

Options:
A Areolar tissue
B Adipose tissue
C Dense connective tissue
D Cartilage.

The correct answer is:
Areolar tissue

Solution:
Loose connective tissue has cells and fibres loosely arranged in a semi-fluid ground substance, for example, areolar tissue present beneath the skin. Often it serves as a support framework for epithelium. It contains fibroblasts (cells that produce and secrete fibres), macrophages, and mast cells. Adipose tissue is a modified areolar tissue located mainly beneath the skin. The cells of this tissue are specialized to store fats. The excess of nutrients that are not used immediately are converted into fats and are stored in this tissue.

Topic: Biology, Structural Organisation in Animals, NEET
Which of the following acts as a bidentate ligand in complex formation

Options:
A Acetate
B Oxalate
C Thiocyanate
D EDTA

The correct answer is:
Oxalate

Solution:
Oxalate, as it makes use of its two atoms to form two co-ordinate covalent bonds with the central metal ion.

Topic: Chemistry, Coordination Compounds, JEE Main
Which of the following acts as an oxidising as well as reducing agent?

Options:
A Na2O
B H2SO4
C HNO3
D HNO2

The correct answer is:
HNO2

Solution:
As in HNO2 , N is in +3 oxidation state but nitrogen can have oxidation states from −3 to +5 so it is in between the maximum and minimum oxidation state hence it can either get reduced or oxidized, depending on the conditions. It means it can act both as an oxidizing and a reducing agent. It can work both as oxidising as well as reducing agent.
(I) As an oxidising agent:
HNO2+2H++e-→NO+H2O
(II) As reducing agent:
HNO2+H2O→NO3-+3H++2e-

Topic: Chemistry, Redox Reactions, JEE Main
Which of the following acts as both reducing and oxidising agents?

Options:
A H2SO4
B HNO3
C H2O2
D KMnO4

The correct answer is:
H2O2

Solution:
In (a), (b) and d; Sulphur, nitrogen and Mn are in their maximum oxidation state, so they can only be reduced and thus can act only as oxidising agent.
(c) only H2O2 will act as both.
(i) In case of oxidising agent
H2O2 itself get reduced:
e.g.,
(ii) In case of reducing agent H2O2 itself get oxidise

Topic: Chemistry, Redox Reactions, JEE Main
Which of the following aestivations involves non-uniform overlapping of petals?

Options:
A Valvate
B Twisted
C Imbricate
D Contorted

The correct answer is:
Valvate

Solution:
Aestivation: The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation. The main types of aestivation are valvate, twisted, imbricate and vexillary . Valvate Aestivation: Petals or Sepals in a whorl merely meet by their edges without overlapping. Example: Sepals of Hibiscus.

Topic: Biology, Morphology of Flowering Plants, NEET
Which of the following alcohol is unable to turn orange colour of chromic acid to green?

Options:
A Primary alcohol
B Secondary alcohol
C Tertiary alcohol
D Allyl alcohol

The correct answer is:
Tertiary alcohol

Solution:
Tertiary alcohol offers resistance to oxidation. Hence, Cr3+ ions are not formed, and the solution does not turn green.

Topic: Chemistry, Alcohols Phenols and Ethers, JEE Main
Which of the following algae produce carrageen?

Options:
A Green algae
B Brown algae
C Red algae
D Blue-green algae

The correct answer is:
Red algae

Solution:
Red algae or Rhodophyceae members are mainly marine forms. The marine brown and red algae produce large amounts of hydrocolloids (water-holding substances), e.g., algin (brown algae) and carrageen or carrageenan (red algae) which are used commercially.

Topic: Biology, Plant Kingdom, NEET, NEET 2021
Which of the following alkali metals is smallest in size

Options:
A $R b$
B K
C $\mathrm{Na}$
D Li

The correct answer is:
Li

Solution:
$L i$ is smallest in size among the alkali metals as it has minimum number of shells.

Topic: Chemistry, s Block Elements, JEE Main
Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?

Options:
A $\mathrm{CaSO}_4$
B $\mathrm{BeSO}_4$
C $\mathrm{BaSO}_4$
D $\mathrm{SrSO}_4$

The correct answer is:
$\mathrm{BeSO}_4$

Solution:
Key Idea Hydration energy varies inversely with size and in sulphates of alkaline earth metals lattice energy remains almost constant. The order of size of alkaline earth metals is
$$
\mathrm{Be}^{2+} < \mathrm{Ca}^{2+} < \mathrm{Sr}^{2+} < \mathrm{Ba}^{2+}
$$
Thus, the order of hydration energy is
$$
\mathrm{Be}^{2+}>\mathrm{Ca}^{2+}>\mathrm{Sr}^{2+}>\mathrm{Ba}^{2+}
$$
Hence, $\mathrm{BeSO}_4$ has the hydration enthalpy higher than the lattice enthalpy.

Topic: Chemistry, s Block Elements, NEET, NEET 2010 (Screening)
Which of the following alkaline earth metals shows some properties similar to aluminium

Options:
A $\mathrm{Be}$
B $\mathrm{Ca}$
C $\mathrm{Sr}$
D $B a$

The correct answer is:
$\mathrm{Be}$

Solution:
Be due to diagonal relationship

Topic: Chemistry, s Block Elements, JEE Main
Which of the following alkaline-earth metal hydroxides is the strongest base

Options:
A $\mathrm{Be}(\mathrm{OH})_2$
B $\mathrm{Mg}(\mathrm{OH})_2$
C $\mathrm{Ca}(\mathrm{OH})_2$
D $\mathrm{Ba}(\mathrm{OH})_2$

The correct answer is:
$\mathrm{Ba}(\mathrm{OH})_2$

Solution:
$\mathrm{Be}(\mathrm{OH})_2 \lt \mathrm{Mg}(\mathrm{OH})_2 \lt \mathrm{Ca}(\mathrm{OH})_2 \lt \mathrm{Sr}(\mathrm{OH})_2 \lt \mathrm{Ba}(\mathrm{OH})_2$
On moving down the group basic character increases.

Topic: Chemistry, s Block Elements, JEE Main
Which of the following alkanes will give a single product with a methylene insertion?

Options:
A Me4C
B CH3CH2CH3
C Me2CHCHMe2
D MeCH2CMe2CH2CH3

The correct answer is:
Me4C

Solution:
Number of methylene insertion product = Type of C−H
As it has only primary H-atoms of same type so only one product is possible
Rest other have different types of H-atoms so different products are possible.

Topic: Chemistry, Hydrocarbons, JEE Main
Which of the following alkene has the slowest rate of hydrogenation?

Options:
A I
B II
C III
D IV

The correct answer is:
III

Solution:
Less stable alkene will be more reactive towards catalytic hydrogenation. Propene is least stable among all due to least hyperconjugation.

Topic: Chemistry, Hydrocarbons, JEE Main
Which of the following alkyl groups has the maximum + / effect

Options:
A $\mathrm{CH}_3-$
B $\left(\mathrm{CH}_3\right)_2 \mathrm{CH}-$
C $\left(\mathrm{CH}_3\right)_3 \mathrm{C}-$
D $\mathrm{CH}_3 \mathrm{CH}_2-$

The correct answer is:
$\left(\mathrm{CH}_3\right)_3 \mathrm{C}-$

Solution:
Increasing + I effect
$\left(\mathrm{CH}_3\right)_3 \mathrm{C}\gt\left(\mathrm{CH}_3\right)_2 \mathrm{CH}\gt\mathrm{CH}_3 \mathrm{CH}_2\gt\mathrm{CH}_3$

Topic: Chemistry, General Organic Chemistry, JEE Main
Which of the following alkyl halides is hydrolysed by SN1 mechanism?

Options:
A CH3Cl
B CH3CH2Cl
C CH3CH2CH2Cl
D CH33CCl

The correct answer is:
CH33CCl

Solution:
SN1 reaction is favoured by stability of carbocation i.e. tertiary > secondary > primary.

Topic: Chemistry, Haloalkanes and Haloarenes, JEE Main
Which of the following amines can be prepared by Gabriel phthalimide reaction?

Options:
A t-butylamine
B n-butylamine
C triethylamine
D neo-pentylamine

The correct answer is:
n-butylamine

Solution:
Gabriel phthalimide is used to prepare primary amine.

In first step SN2 reaction takes place which is possible in less stearically hindered chloride. Alkyl chloride required for other amines has high stearic hindrance therefore, stearically hindered amine can't be produced from those alkyl chlorides.

Topic: Chemistry, Amines, JEE Main, JEE Main 2019 (08 Apr Shift 1)
Which of the following amines give mustard oil smell with HgCl2+CS2 ?
(I) Aniline
(II) Diethyl amine
(III) P-toluidine
(IV) N,N-Diethyl propanamine

Options:
A (I) & (II)
B (II) & (IV)
C (II) & (III)
D (I) & (III)

The correct answer is:
(I) & (III)

Solution:
Primary amine such as aniline and P-toluidine gives mustard oil test.

Topic: Chemistry, Amines, JEE Main
Which of the following amino acids is basic in nature?

Options:
A Valine
B Tyrosine
C Arginine
D Leucine

The correct answer is:
Arginine

Solution:
Arginine consists of amine group as the functional group. Hence, is basic in nature.

Topic: Chemistry, Biomolecules, JEE Main
Which of the following animal is not viviparous?

Options:
A Flying fox (Bat)
B Elephant
C Platypus
D Whale

The correct answer is:
Platypus

Solution:
Platypus is an oviparous mammal i.e. it lays eggs whereas the remaining are viviparous i.e. they give birth to young ones.

Topic: Biology, Animal Kingdom, NEET, NEET 2015 (Phase 1)
Which of the following aqueous solutions will exhibit highest boiling point?

Options:
A $0.01 \mathrm{M}$ urea
B $0.01 \mathrm{M} \mathrm{KNO}_{3}$
C $0.01 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}$
D $0.015 \mathrm{M} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$

The correct answer is:
$0.01 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}$

Solution:
$\begin{aligned}
\mathrm{NH}_{2} \mathrm{CONH}_{2} & \longrightarrow \text { no dissociation } \\
\mathrm{KNO}_{3} & \longrightarrow \mathrm{K}^{+}+\mathrm{NO}_{3}^{-} ; \quad i=2 \\
\mathrm{Na}_{2} \mathrm{SO}_{4} & \longrightarrow 2 \mathrm{Na}^{+}+\mathrm{SO}_{4}^{2-} ; \quad i=3 \\
\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} & \longrightarrow \text { no dissociation }
\end{aligned}$
As $\mathrm{Na}_{2} \mathrm{SO}_{4}$ gives maximum particles, i.e., 3 on dissociation boiling point is maximum for $\mathrm{Na}_{2} \mathrm{SO}_{4}$.

Topic: Chemistry, Solutions, JEE Main
Which of the following are arranged in an increasing order of their bond strengths ?

Options:
A
$\mathrm{O}_2^{-} < \mathrm{O}_2 < \mathrm{O}_2^{+} < \mathrm{O}_2^{2-}$
B
$\mathrm{O}_2^{2-} < \mathrm{O}_2^{-} < \mathrm{O}_2 < \mathrm{O}_2^{+}$
C
$\mathrm{O}_2^{-} < \mathrm{O}_2^{2-} < \mathrm{O}_2 < \mathrm{O}_2^{+}$
D
$\mathrm{O}_2^{+} < \mathrm{O}_2 < \mathrm{O}_2^{-} < \mathrm{O}_2^{2-}$

The correct answer is:
$\mathrm{O}_2^{2-} < \mathrm{O}_2^{-} < \mathrm{O}_2 < \mathrm{O}_2^{+}$

Solution:
According to bond order values the given order is the answer. Bond order values are
$+1,+1 \frac{1}{2},+2$ and $+2 \frac{1}{2}$, higher bond order means stronger bond.

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main, JEE Main 2002
Which of the following are arranged in the decreasing order of dipole moment?

Options:
A CH3Cl,CH3Br,CH3F
B CH3Cl,CH3F,CH3Br
C CH3Br,CH3Cl,CH3F
D CH3Br,CH3F,CH3Cl

The correct answer is:
CH3Cl,CH3F,CH3Br

Solution:
The values of dipole moments of methyl halides
CH3F 1.51 D; CH3Cl 1.56 D
CH3Br 1.4 D; CH3I 1.29 D
CH3Cl>CH3F>CH3Br>CH3I

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main
Which of the following are characteristics of a sporophyte of Bryophytes?

I. Multicellular sporophyte.

II. Completely or partially dependent on the gametophyte.

III. Undergoes a reduction division to form spores.

Options:
A II and III
B III and I
C Only I
D All of these

The correct answer is:
All of these

Solution:
In Bryophyta main plant body is a gametophyte and sporophyte is produced after sexual reproduction. The sporophyte is multicellular which remain attached to gametophyte and derives its nutrition completely or partially. Sporogenous cells present inside the capsule of sporophyte undergoes reduction division to form haploid spores.

Topic: Biology, Plant Kingdom, NEET
Which of the following are characteristics of physisorption?
a. Weak attractive interactions between adsorbate and adsorbent
b. Monolayer formation of adsorbent on adsorbate
c. Remains unaffected by change of temperature
d. Decreases with increase of temperature
e. It is also known as activated adsorption

Options:
A \( \mathrm{b}, \mathrm{c} \& \mathrm{e} \) but not \( \mathrm{a} \& \mathrm{~d} \)
B \( \mathrm{a}, \mathrm{b} \& \mathrm{~d} \) but not \( \mathrm{c} \& \mathrm{e} \)
C \( \mathrm{a} \& \mathrm{~d} \) but not \( \mathrm{b}, \mathrm{c} \& \mathrm{e} \)
D \( \mathrm{a}, \mathrm{b} \& \mathrm{e} \) but not \( \mathrm{c} \& \mathrm{~d} \)

The correct answer is:
\( \mathrm{a} \& \mathrm{~d} \) but not \( \mathrm{b}, \mathrm{c} \& \mathrm{e} \)

Solution:
There are five statements in the question we will check all the statements one by one whether it is correct or not.

STATEMENT a — It is correct because there are weak Van der Waal's forces of attraction between adsorbate and adsorbent.

STATEMENTb — It is an incorrect statement because physisorption is multilayer formation of adsorbent on adsorbate.

STATEMENT c— It is incorrect because as physisorption is dependent upon temperature.

STATEMENT d — It is correct because physisorption is inversely proportional to the temperature.

STATEMENT e— It is incorrect because chemisorption is also known as activated adsorption, not physisorption.

Topic: Chemistry, Surface Chemistry, JEE Main
Which of the following are common components of photochemical smog?
1. Chlorofluorocarbons
2. Acrolein
3. Ozone
4. Peroxyacetyl nitrate

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

The correct answer is:
2, 3, 4

Solution:
The common components of photochemical smog are Ozone, Nitric oxide, Acrolein, Formaldehyde
and Peroxyacehyl nitrate (PAN).
Hence Chlorofluorocarbons (CFC) is not common component of photochemical smog.

Topic: Chemistry, Environmental Chemistry, JEE Main
Which of the following are correct?
(i) First ionisation enthalpy of $\mathrm{He} < $ Second ionization enthalpy of Li.
(ii) Li has the highest second ionisation enthalpy.
(iii) All $d$-block elements are transition elements.
(iv) The only alphabet not found in the periodic table is the letter ' $\mathrm{J}$ '.
(v) Francium concentration is $\sim 10^{-18} \mathrm{ppm}$ on Earth.

Options:
A (i), (ii), (iv)
B (i), (ii), (iv), (v)
C (i), (ii), (v)
D (iv), (v)

The correct answer is:
(i), (ii), (iv), (v)

Solution:
All transition elements are $d$-block elements but all $d$-block elements are not transition metals. A transition metal is one which forms one or more stable ions which have incomplete $d$-orbitals. On the basis of this definition, scandium and zinc do not count as transition metal although they are d-block elements.
Thus, statement (3) is incorrect.

Topic: Chemistry, Classification of Elements and Periodicity in Properties, JEE Main
Which of the following are Lewis acids?

Options:
A BCl3 and AlCl3
B PH3 and BCl3
C AlCl3 and CCl4
D PH3 and CCl4

The correct answer is:
BCl3 and AlCl3

Solution:
Both BCl3 and AlCl3 have vacant p-orbital and incomplete octet. So they accept lone pair and act as Lewis acids.

Topic: Chemistry, Ionic Equilibrium, JEE Main, JEE Main 2018 (08 Apr)
Which of the following are not a constant value between two given thermodynamic states of a given system?

(I) q+w

(II) q

(III) w

(IV) H-TS

Options:
A (I) and (IV)
B (II), (III) and (IV)
C (I), (II) and (III)
D (II) and (III)

The correct answer is:
(II) and (III)

Solution:
We know that q (heat) and w (work) aren't state functions but dv=dq+dw is a state function.
H - TS (i.e. G) is also a state function.
Thus II and III are not state functions so the correct answer is option (D).

Topic: Chemistry, Thermodynamics (C), JEE Main
Which of the following are not characteristic features of Fabaceae?

Options:
A Tap root system, compound leaves and raceme inflorescence
B Flowers actinomorphic, twisted aestivation and gamopetalous
C Stamens ten, introrse, basifixed and dithecous
D Monocarpellary, ovary superior and bent stigma

The correct answer is:
Flowers actinomorphic, twisted aestivation and gamopetalous

Solution:
Fabaceae or leguminosae are the third largest family of angiosperms. The main characters of this family are polypetalous condition, single carpel (monocarpellary condition), perigynous condition and marginal placentation, tap root system, simple or compound leaves, racemose, inflorescence, zygomorphic flowers, imbricate aestivation, stamens 10, introrse and fruit is legume or pod.

Topic: Biology, Morphology of Flowering Plants, NEET