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1

JEE Main 2019 (Online) 12th January Morning Slot

MCQ (Single Correct Answer)
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

Explanation

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

Rb + O2 $$ \to $$ RbO2

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

JEE Main 2019 (Online) 11th January Evening Slot

MCQ (Single Correct Answer)
The reaction that does NOT define calcination is :
A
2Cu2S + 3O2 $$\buildrel \Delta \over \longrightarrow $$ 2Cu2O + 2SO2
B
CaCO3 . MgCO3 $$\buildrel \Delta \over \longrightarrow $$ CaO + MgO + 2CO2
C
ZnCO3 $$\buildrel \Delta \over \longrightarrow $$ ZnO + CO2
D
Fe2O3 . XH2O $$\buildrel \Delta \over \longrightarrow $$ Fe2O3 + XH2O

Explanation

Calcination involves heating of the ore in absence of air.

2Cu2S + 3O2 $$\buildrel \Delta \over \longrightarrow $$ 2Cu2O + 2SO2 $$ \uparrow $$

This reaction involve roasting. Roasting is carried out mainly for sulphide ores in presence of excess of oxygen.
3

JEE Main 2019 (Online) 11th January Evening Slot

MCQ (Single Correct Answer)
Match the following items in column I with the corresponding items in column II.

Item I Item II
(i) Na2CO3.10H2O (A) Portland cement ingredient
(ii) Mg(HCO3)2 (B) Castner-Kellner process
(iii) NaOH
(C) Solvay process
(iv) Ca3Al2O6 (D) Temporary hardness
A
(i)$$ \to $$(D); (ii)$$ \to $$(A); (iii)$$ \to $$(B); (iv)$$ \to $$(C)
B
(i)$$ \to $$(B); (ii)$$ \to $$(C); (iii)$$ \to $$(A); (iv)$$ \to $$(D)
C
(i)$$ \to $$(C); (ii)$$ \to $$(B); (iii)$$ \to $$(D); (iv)$$ \to $$(A)
D
(i)$$ \to $$(C); (ii)$$ \to $$(D); (iii)$$ \to $$(B); (iv)$$ \to $$(A)

Explanation

Na2CO3.10H2O $$ \to $$ Solvay process

Mg(HCO3)2 $$ \to $$ Temporary hardness

NaOH $$ \to $$ Castner-kellner cell

Ca3Al2O6 $$ \to $$ Portland cement
4

JEE Main 2019 (Online) 11th January Morning Slot

MCQ (Single Correct Answer)
The amphoteric hydroxide is :
A
Ca(OH)2
B
Be(OH)2
C
Mg(OH)2
D
Sr(OH)2

Explanation

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

Questions Asked from s-Block Elements

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