Periodic Table & Periodicity

JEE Chemistry · 270 questions · Page 14 of 27 · Click an option or "Show Solution" to reveal answer

Q131

Both lithium and magnesium display several similar properties due to the diagonal relationship; however, the one which is incorrect, is :

A both form soluble bicarbonates

B both from nitrides

C nitrates of both Li and Mg yield NO2 and O2 on heating

D both form basic carbonates

Correct Answer

Option D

Solution

Mg can form basic carbonate like 3MgCO3 . Mg(OH)2 . 3H2O While Li can not.

Q132

The INCORRECT statement is :

A Lithium is least reactive with water among the alkali metals

B LiCl crystallises from aqueous solution as LiCl.2H2O

C Lithium is the strongest reducing agent among the alkali metals

D LiNO3 decomposes on heating to give LiNO2 and O2

Correct Answer

Option D

Solution

LiNO3

\overset{\Delta}\longrightarrow

Li2O + NO2 + O2 Ionic potential of Li is high that is why on thermal demoposition of nitrate form of Li will give oxide of Li and NO2 and O2.

Q133

The reaction that does NOT define calcination is :

A 2Cu2S + 3O2

\overset{\Delta}\longrightarrow

2Cu2O + 2SO2

B CaCO3 . MgCO3

\overset{\Delta}\longrightarrow

CaO + MgO + 2CO2

C ZnCO3

\overset{\Delta}\longrightarrow

ZnO + CO2

D Fe2O3 . XH2O

\overset{\Delta}\longrightarrow

Fe2O3 + XH2O

Correct Answer

Option A

Solution

Calcination involves heating of the ore in absence of air. 2Cu2S + 3O2

\overset{\Delta}\longrightarrow

2Cu2O + 2SO2 $\uparrow$ This reaction involve roasting.

Roasting is carried out mainly for sulphide ores in presence of excess of oxygen.

Q134

A metal on combustion in excess air forms X. X upon hydrolysis with water yields H2O2 and O2 along with another product. The metal is :

A Rb

B Mg

C Na

D Li

Correct Answer

Option A

Solution

K, Rb and Cs form super oxides on reaction with excess air.

Rb + O2 $\to$ RbO2 2RbO2 + 2H2O $\to$ 2RbOH + H2O2 + O2 $\uparrow$

Q135

The alkaline earth metal nitrate that does not crystallise with water molecules, is :

A Mg(NO3)2

B Sr(NO3)2

C Ca(NO3)2

D Ba(NO3)2

Correct Answer

Option D

Solution

When central atom size is smaller then more water molecule will crystallize.

Ba(NO3)2 does not ctystallize with water as size of Ba+2 ion is very large.

Q136

The metal that forms nitride by reacting directly with N2 of air, is :

A K

B Li

C Rb

D Cs

Correct Answer

Option B

Solution

Only Li react directly with N2 out of alkali metals 6 Li + N2 $\to$ 2Li3N

Q137

Sodium metal on dissolution in liquid ammonia gives a deep blue solution due to the formation of :

A ammoniated electrons

B sodamide

C sodium-ammonia complex

D sodium ion-ammonia complex

Correct Answer

Option A

Solution

Na + (x + y)NH3(

l

) $\to$ [Na(NH3)x]+ + [e(NH3)y]- [e(NH3)y]- is called solvated or ammoniated electron.

Q138

The amphoteric hydroxide is :

A Ca(OH)2

B Be(OH)2

C Mg(OH)2

D Sr(OH)2

Correct Answer

Option B

Solution

Be(OH)2 is amphoteric in nature while rest all alkaline earth metal hydroxide are basic in nature.

Q139

When gypsum is heated to 393 K, it forms :

A CaSO4 . 0.5H2O

B CaSO4 . 5H2O

C Dead burnt plaster

D Anhydrous CaSO4

Correct Answer

Option A

Solution

CaSO4.2H2O (Gypsum)

\overset{{393K}}\longrightarrow

CaSO4.

{1 \over 2}

H2O(Plaster of paris) +

{3 \over 2}

H2O

Q140

Among the statements (a)-(d) the correct ones are : (a) Lithium has the highest hydration enthalpy among the alkali metals. (b) Lithium chloride is insoluble in pyridine. (c) Lithium cannot form ethynide upon its reaction with ethyne. (d) Both lithium and magnesium react slowly with H2O.

A (b) and (c) only

B (a) and (d) only

C (a), (b) and (d) only

D (a), (c) and (d) only

Correct Answer

Option D

Solution

Lithium has highest hydration enthalpy among alkali metals due to its small size.

LiCl is soluble in pyridine because LiCl have more covalent character.

Li does not form ethynide with ethyne.

Both Li and Mg reacts slowly with H2O.

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