JEE Main Previous Year Papers Questions With Solutions Chemistry Elements of S-Block : Hydrogen,Group 1 and 2

JEE Main Previous Year Papers Questions With Solutions Chemistry  Elements of S-Block : Hydrogen, Group 1 and 2

1.K0₂(potassium super oxide) is used in oxygen cylinders in space and submarines. This is because it        (2002)
(1)absorbs C0₂ and increases 0₂ content
(2)eliminates moisture
(3)absorbs C0₂ 4) produces ozone
Ans.(2) 2KO, + 2H₂0 —>2KOH + H₂0₂ + 0₂. Eliminates moisture.

2.A metal M readily forms its sulphate MS0₄which is water soluble. It forms its oxide MO which becomes inert on heating. It forms an insoluble hydroxide M(OH)₂ which is soluble in NaOH solution. Then M is     (2002)
(1)Mg 2) Ba 3) Ca 4) Be
Ans.(4) Beryllium shows anomalous properties with alkaline earth metals, due to its small size.

3.In curing cement plasters water is sprinkled from time to time. This helps in           (2003)
(1)developing interlocking needle-like crystals of hydrated silicates.
(2)hydrating sand and gravel mixed with cement
(3)converting sand into silicic acid
(4)keeping it cool
Ans.(1) Cross links are developed during hydration of calcium aluminosilicates.

4.The substance not likely to contain CaC0₃ is
(1)calcined gypsum 2) sea shells (2003) 3) dolomite 4) a marble statue
Ans.(1) The composition of gypsum is CaS0₄. 2H₂0, while others are carbonates.

5.The solubilities of carbonates decrease down the magnesium group. This is due to a decrease in
(1)hydration energies of cations (2003)
(2)inter – ionic attraction
(3)entropy of solution formation
(4)lattice energies of solids
Ans.(1) The solubility is governed by AH _soIution
AH solution^– AH_lattjce_ AH_Hydration.
Due to increase in size, the magnitude of hydration energy decreases and hence the solubility.

6.Several blocks of magnesium are fixed to the bottom of a ship to          (2003)
(1)make the ship lighter
(2)prevent action of water and salt
(3)prevent puncturing by under-sea rocks
(4)keep away the sharks
Ans.(2) Magnesium provides cathodic protection and prevent rusting or corrosion.

7.Which one of the following processes willproduce hard water ?      (2003)
(1)Saturation of water with MgCO_a
(2)Saturation of water with CaS0₄
(3)Addition of Na₂S0₄ to water
(4)Saturation of water with CaC0₃
Ans.(2) Permanent hardness of water is due to chlorides and sulphates of calcium and magnesium.

8.In hydrogen – oxygen fuel cell, combustion of hydrogen occurs to      (2004)
(1)generate heat
(2)remove adsorbed oxygen from electrode surfaces
(3)produce high purity water
(4)create potential difference between the two electrodes Ans.(4) Heat is converted directlyto electricity.
Ans.(4) Heat is converted directlyto electricity.

9.One mole of magnesium nitride on the reaction with an excess of water gives (2004)
(1)one mole of ammonia
(2)two moles of nitric acid
(3)two moles of ammonia
(4)one mole of nitric acid
Ans.(3) Mg₃N₂ +6H₂0——– » 3Mg(OH)₂ + 2NH₃

10.Hydrogen bomb is based on the principle of
(1)Nuclear fission (2005)
(2) Natural radioactivity
(3) Nuclear fusion
(4)Artificial radioactivity
Ans.(3) Fusion of isotopes of hydrogen.

11.Based on lattice energy and other considerations which one of the following alkali metal chlorides is expected to have the highest melting point.(2005)
1) LiCl       2) NaCl       3) KC1       4) RbCl
Ans.(2) Although lattice energy of LiCl higher than NaCl, but LiCl is covalent in nature and NaCl ionic. There after, the melting point decreases as we move NaCl because the lattice energy decreases as size of alkali metal atom increases. Higher lattice energy denotes higher melting and boiling points.

12.The ionic mobility of alkali metal ions in aqueous solution is maximum for (2006)
1) K⁺   2) Rb⁺  3) Li⁺   4) Na⁺
Ans.(2) Hydrated Rb⁺ has small size.

13.In context with the industrial preparation of hydrogen from water gas (CO+H₂), Which of  the following is the correct statement ? (2008)
(1)CO and H₂ are fractionally separated using differences in their densities
(2)CO is removed by absorption in aqueous Cu₂Cl₂ solution
(3)H₂ is removed through occulsion with Pd
(4)CO is oxidised to C0₂ with steam in the presence of a catalyst followed by absorption of C0₂ in alkali
Ans.

14. Very pure hydrogen (99.9%) can be made by ’ which of the following processes ?   (2012)
(1)Reaction of methane with steam
(2)Mixing natural hydrocarbons of high molecular weight
(3) Elecrolysis of water
(4)Reaction of salt like hydrides with water
Ans.

15.The first ionization potential of Na is 5.1 eV. The value of electron gain enthalpy of Na⁺ will be (2013)
1) -2.55 eV                   2) -5.1 eV
3)-10.2 eV                    4) +2.55 eV
Ans.(2) Inisation potential of alkali metal atom and electron affinity of its monocovalent cation are same in magnitude, but with opposite signs.

16.The metal that cannot be obtained by electrolysis of an aqueous solution of its salt is       (2014)
1) Cr 2) Ag 3) Ca 4) Cu
Ans.(3) Ca canot be obtained by the electrolysis of aqueous solution of its salt.

17.In which of the following reactions H₂0₂ acts as reducing agent ?     (2014)
a.H₂0₂ + 2H⁺ + 2e- -> 2H₂0
b.H₂0₂ – 2e–> 0₂ + 2H⁺
c.H₂0₂ + 2e- -> 20H-
d.H₂0₂ + 20H- 2e- -> 0₂ + 2H₂0
1) (b), (d)    2) (a), (b)      3) (c), (d)    4) (a), (c)
Ans.(1) While acting as reducing agent it gives up electrons and release oxygen gas.

Ans. 4) 2 mol of water softener require one mole of Ca²⁺

19.Form the following statements regarding H₂0₂, choose the incorrect statement (2015)
(1)It can act only as an oxidizing agent
(2)It decompose on exposure to light
(3)It has to be stored in plastic or was lined glass bottles in dark
(4)It has to be kept away form dust
Ans.(1) It is disproportionating agent.

20.Which one of the following alkaline earthmetal sulphates has its hydration enthalpy greater than its lattice enthalpy ?        (2015)
1) CaS0₄ 2) BeS0₄ 3) BaS0₄ 4) SrS0₄
Ans.(2) Among alkaline earth metal sulphates BeS0₄ and MgS0₄ are water soluble due to high hydration enthalpy of Be²⁺ and Mg²⁺.