Periodic Table & Periodicity — Page 2 | JEE Chemistry

Q11

Which pair of oxides is acidic in nature?

A CaO, SiO2

B B2O3, CaO

C B2O3, SiO2

D N2O, BaO

Correct Answer

Option C

Solution

B2O3 and SiO2 both are oxides of non-metal and hence are acidic in nature.

Q12

The difference between electron gain enthalpies will be maximum between :

A Ar and Cl

B Ne and Cl

C Ne and F

D Ar and F

Correct Answer

Option B

Solution

$\Delta \mathrm{H}_{\mathrm{eg}}$ for chlorine $=-349 \mathrm{~kJ} \mathrm{~mole}^{-1}$ $\Delta \mathrm{H}_{\mathrm{eg}}$ for Neon $=+116 \mathrm{~kJ} \mathrm{~mole}^{-1}$

Q13

The commercial name for calcium oxide is :

A Milk of lime

B Slaked lime

C Limestone

D Quick lime

Correct Answer

Option D

Solution

The commercial name of calcium oxide (CaO) is quick lime.

Q14

Reaction of BeO with ammonia and hydrogen fluoride gives A which on thermal decomposition gives

\mathrm{BeF_2}

and

\mathrm{NH_4F}

. What is 'A'?

A

\mathrm{(NH_4)Be_2F_5}

B

\mathrm{(NH_4)_2BeF_4}

C

\mathrm{(NH_4)BeF_3}

D

\mathrm{H_3NBeF_3}

Correct Answer

Option B

Solution

\mathrm{BeO}+\mathrm{NH}_{3}+\mathrm{HF} \longrightarrow\left(\mathrm{NH}_{4}\right)_{2} \underset{(\mathrm{A})}{\mathrm{BeF}_{4}} \stackrel{\Delta}{\longrightarrow} \mathrm{BeF}_{2}+\mathrm{NH}_{4} \mathrm{~F}

Compound $\mathrm{A}$ is $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{BeF}_{4}$

Q15

The ionic radii of O2–, F–, Na+ and Mg2+ are in the order :

A F– > O2– > Na+ > Mg2+

B Mg2+ > Na+ > F– > O2–

C O2– > F– > Mg2+ > Na+

D O2– > F– > Na+ > Mg2+

Correct Answer

Option D

Solution

Among isoelectronic species, greater the Zeff smaller will be the radius.

Order of Zeff : Mg2+ > Na+ > F– > O2– Order of Ionic Radii : O2– > F– > Na+ > Mg2+

Q16

For Na+, Mg2+, F- and O2-; the correct order of increasing ionic radii is :

A O2- < F- < Na+ < Mg2+

B Na+ < Mg2+ < F- < O2-

C Mg2+ < Na+ < F- < O2-

D Mg2+ < O2- < Na+ < F-

Correct Answer

Option C

Solution

Here all of them are isoelectric.

For isoelectric anion size is more than cation.

Among two anions which anion has more negative charge will have more radius and among two cation which cation has less positive charge will have more radius.

Q17

The metal used for marking X–ray tube window is :

A Ca

B Na

C Mg

D Be

Correct Answer

Option D

Solution

''Be'' Metal is used in x-ray window is due to transparent to x-rays.

Q18

An alkaline earth metal ‘M’ readily forms water soluble sulphate and water insoluble hydroxide. Its oxide MO is very stable to heat and does not have rock-salt structure. M is :

A Ca

B Mg

C Sr

D Be

Correct Answer

Option D

Solution

BeSO4 is water soluble. Be(OH)2 is water insoluble. BeO is stable to heat.

Q19

Among the sulphates of alkaline earth metals, the solubilities of BeSO4 and MgSO4 in water, respectively, are :

A poor and poor

B poor and high

C high and poor

D high and high

Correct Answer

Option D

Solution

Order of solubility of sulphate of Alkaline earth metals BeSO4 > MgSO4 > CaSO4 > SrSO4 > BaSO4 The greater hydration enthalpies of Be2+ and Mg2+ ions dominate over their lattice enthalpies and therefore their sulphates are highly soluble.

Q20

The number of water molecules in gypsum, dead burnt plaster and plaster of Paris, respectively are :

A 2, 0 and 1

B 0.5, 0 and 2

C 5, 0 and 0.5

D 2, 0 and 0.5

Correct Answer

Option D

Solution

Gypsum

CaS{O_4}.2{H_2}O

Plaster of Paris

CaS{O_4}.{1 \over 2}{H_2}O

Dead burnt plaster

CaS{O_4}