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Chemistry MCQs for NEET — Practice Questions with Answers

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The correct order of atomic/ionic radii is:

$S c > T i > V > C r$

$C o > N i > C u > Z n$

$S^{2 -} > C l^{-} > O^{2} > N^{3 -}$

None of these

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Explanation

(a) (a) Sc > Ti > V > Cr (size decrease initially in 3d-series)

(b) Correct order : Zn > Cu > Co $\approx$ Ni

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Which of the following transformation least energy is required?

${F^{-}}_{(g)} \to F_{(g)} + e^{-}$

${P^{-}}_{(g)} \to P_{(g)} + e^{-}$

${S^{-}}_{(g)} \to S_{(g)} + e^{-}$

$C {l^{-}}_{(g)} \to C l_{(g)} + e^{-}$

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Explanation

(b) If we consider the opposite process:

$(a) F_{(g)} + e^{-} \to {F^{-}}_{(g)}; ∆ H_{1} (b) P_{(g)} + e^{-} \to {P^{-}}_{(g)}; ∆ H_{2} (c) S_{(g)} + e^{-} \to {S^{-}}_{(g)}; ∆ H_{3} (d) C l_{(g)} + e^{-} \to C {l^{-}}_{(g)}; ∆ H_{4} O r d e r o f e n e r g y r e l e a s e s i s : ∆ H_{4} > ∆ H_{1} > ∆ H_{3} > ∆ H_{2}$

$S o, {P^{-}}_{(g)} \to e^{‐}; R e q u i r e s l e a s t e n e r g y .$

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Which of the following represents correct order of electron affinity?

Cl>F>S>O

F>O>S>Cl

F>Cl>S>O

Cl>S>O>F

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Explanation

(a) Correct order of electron affinity is : Cl>F>S>O

Electron affinity of 2nd period non-metals is less than that of respective 3rd period non-metals.

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Correct expression of "Allred and Rochow's" scale is:

Electronegativity = $0.744 \frac{Z_{e f f .}}{r^{2}} + 0.359$

Electronegativity = $0.359 \frac{r^{2}}{Z_{e f f .}} + 0.744$

Electronegativity = $0.359 \frac{Z_{e f f .}}{r} + 0.744$

Electronegativity = $0.359 \frac{Z_{e f f .}}{r^{2}} + 0.744$

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Explanation

(d) According to Allred and Rochow scale

Electronegativity = $0.359 \frac{Z_{e f f .}}{r^{2}} + 0.744$

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The process requiring absorption of energy is:

$N \to N^{-}$

$F \to F^{-}$

$C l \to C l^{-}$

$H \to H^{-}$

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Explanation

(a) Nitrogen has stable $2 p^{3}$ configuration and also due to high $e^{-}$ charge density at outermost orbital it requires energy to add one extra $e^{-}$ in its outer most shell i.e., its first electron gain enthalpy is positive.

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Which of the following compounds has a positive enthalpy of solution?

LiF

LiCl

LiBr

Lil

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Explanation

(a) LiF is sparingly soluble at room temperature due to its high lattice energy.

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Which of the following compound is most acidic?

$C l_{2} O_{7}$

$P_{4} O_{10}$

$S O_{3}$

$B_{2} O_{3}$

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Explanation

(a) Oxidation state of non- metal increases acidic nature of oxide increase $\overset{+ 7}{C l_{2} O_{7}}$ is most acidic.

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A compound contains three elements A, B and C, if the oxidation number of A =+2, B =+5 and C =-2, the possible formula of the compound is :

$A_{3} {(B_{4} C)}_{2}$

$A_{3} {(B C_{4})}_{2}$

$A_{2} {(B C_{3})}_{2}$

$A B C_{2}$

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Explanation

(b) Sum of oxidation numbers of all atoms in a neutral molecule is zero.

$\to A_{3} {(B_{4} C)}_{2} : + 2 \times 3 + 2 \times [4 \times 5 - 2] = 42 \neq 0 \to A_{3} {(B C_{4})}_{2} : + 2 \times 3 + 2 \times [+ 5 - 8] = 0 \to A_{2} {(B C_{3})}_{2} : + 2 \times 2 + 2 \times [+ 5 - 6] = + 2 \neq 0 \to A B C_{2} : + 2 + 5 + (- 2) \times 2 = + 3 \neq 0$

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If period number and group number of any representative element(s) are same then which of the following statement is incorrect regarding such type element(s) in their ground state? (Period number and group number are according to modern form of periodic table)

The possible value of principal quantum number is 2

The possible value of azimuthal quantum number is zero

The possible value of magnetic quantum number is 1

The species could be paramagnetic

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Explanation

(i) H 1 1 $1 s^{1}$

(ii) Be 2 2 $1 s^{1} 2 s^{2}$

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Which of the following properties of the alkaline earth metals increase from Be to Ba?

(i) Atomic radius (ii) Ionisation energy (iii) Nuclear charge

(i) and (ii)

(i) and (iii)

(ii) and (iii)

(i), (ii) and (iii)

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Explanation

(b) Atomic radius and nuclear charge increases from top to bottom because number of shell and atomic mass increases down the group.

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