JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE

JEE: JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE

The document JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE is a part of the JEE Course Chemistry for JEE.
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Q.1. Oxidation number of potassium in K2O, K2O2 and KO2, respectively, is    (2020)
(1) +2, +1 and + 1/2
(2) +1, +1, and +1
(3) +1, +4 and +2
(4) +1, +2 and +4
Ans.
(2)
The oxidation state of potassium is +1 irrespective of nature of oxide.

Q.2. When gypsum is heated to 373 K, it forms    (2020)
(1) Anhydrous CaSO4
(2) CaSO4, 5H2O
(3) CaSO4, 0.5H2O
(4) Dead burnt plaster
Ans.
(3)
The reaction involved is
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE

Q.3. Among the statements (I)-(IV), the correct ones are
(I) Lithium has the highest hydration enthalpy among the alkali metals.
(II) Lithium chloride is insoluble in pyridine.
(III) Lithium cannot form ethynide upon it's reaction with ethyne.
(IV) Both lithium and magnesium react slowly with H2O.    (2020)
(1) (I), (II) and (IV) only
(2) (I), (III) and (IV) only
(3) (II) and (III) only
(4) (I) and (IV) only
Ans.
(2)
(i) Due to small size, Li has high hydration enthalpy.
(ii) Since, the solvation energy of LiCl is higher than the other chloride of the alkali metal. Thus, Licl is soluble in pyridine.
(iii) Due to the small size and high polarizability, Li does not react with ethyne to form ethynide.
(iv) Li and Mg show diagonal relationships. Thus, both react slowly with water.

Q.4. The alkaline earth metal nitrate that does not crystallise with water molecules, is:    (2019)
(1) Mg(NO3)2
(2) Sr(NO3)2
(3) Ca(NO3)2
(4) Ba(NO3)2
Ans.
(4)
The chances of formation of hydrate decreases with the decrease in the charge density down the group. This is why, Ba(NO3)2 does not crystallise with water molecules.

Q.5. The metal that forms nitride by reacting directly with N2 of air, is:    (2019)
(1) K
(2) Li
(3) Rb
(4) Cs
Ans.
(2)
Amongst the given alkali metals, only lithium can react with Nin air to form lithium nitride.

Q.6. The metal used for making X-ray tube window is:    (2019)
(1) Mg
(2) Na
(3) Be
(4) Ca
Ans.
(3)
Be is transparent to X-rays, so it is used in making X-ray tube windows.

Q.7. Sodium metal on dissolution in liquid ammonia gives a deep blue solution due to the formation of:    (2019)
(1) sodium-ammonia complex
(2) sodamide
(3) sodium ion-ammonia complex
(4) ammoniated electrons
Ans.
(4)
Sodium metal on dissolution in liquid ammonia gives a deep blue solution due to the ammoniated electrons.

Q.8. NaH is an example of:    (2019)
(1) Electron-rich hydride
(2) Metallic hydride
(3) Saline hydride
(4) Molecular hydride
Ans.
(3)
NaH is an ionic hydride which is also known as saline hydride.

Q.9. The amphoteric hydroxide is:    (2019)
(1) Be(OH)2
(2) Ca(OH)2
(3) Mg(OH)2
(4) Sr(OH)2
Ans.
(1)
Be(OH)2 is amphoteric in nature.

Q.10. A metal on combution in excess of air forms X. X upon hydrolysis with water yields H2O2 and O2 along with another product. The metal is:    (2019)
(1) Na
(2) Rb
(3) Mg
(4) Li
Ans.
(2)
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE

Q.11. The correct order of hydration enthalpies of alkali metal ions is:    (2019)
(1) Li+ > Na+ > K+ > Cs+ > Rb+
(2) Na+ > Li+ > K+ > Rb+ > Cs+
(3) Na+ > Li+ > K+ > Cs+ > Rb+
(4) Li+ > Na+ > K+ > Rb+ > Cs+
Ans. 
(4)
Hydration energy is inversely proportional to the size of ion.
Li+ < Na< K+ < Rb+ < Cs+- Size
Li+ > Na+ > K+ > Rb+ > Cs+- Hydration energy

Q.12. The covalent alkaline earth metal halide (X = Cl, Br, I) is:    (2019)
(1) MgX2 
(2) CaX2 
(3) BeX2 
(4) SrX2
Ans.
(3)
According to Fajan’s rule, greater the polarising power of cation greater would be the covalent character.
Since, Be2+ has maximum polarising power among given cations. Therefore, BeX2 would be most covalent alkaline earth metal halides among the given halides.

Q.13. The element having greatest difference between its first and second ionization energies, is:    (2019)
(1) Ca
(2) Sc
(3) Ba
(4) K
Ans.
(4)
Alkali metals have high difference in the first and second ionisation energy as they achieve stable noble gas configuration after first ionisation.

Q.14. Magnesium powder bums in air to give:    (2019)
(1) Mg(NO3)2 and Mg3N2
(2) MgO and Mg3N2
(3) MgO only
(4) MgO and Mg(NO3)2
Ans.
(2)
Mg burns in air and produces a mixture of nitride and oxide

Q.15. The structures of beryllium chloride in the solid state and vapour phase, respectively, are:    (2019)
(1) chain and chain
(2) dimeric and dimeric
(3) chain and dimeric
(4) dimeric and chain
Ans. 
(3)
BeCl2 in vapour phase exists as dimer (below 1200 K. temperature) whereas, in solid state BeCl2 has chain structure.

Q.16. A hydrated solid X on heating initially gives a monohydrated compound Y. Y upon heating above 373 K leads to an anhydrous white powder Z. X and Z, respectively, are:    (2019)
(1) Washing soda and soda ash
(2) Baking soda and dead burnt plaster
(3) Washing soda and dead burnt plaster
(4) Baking soda and soda ash
Ans.
(1)
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE
X = Washing soda
Z = Soda ash

Q.17. The metal that gives hydrogen gas upon treatment with both acid as well as base is:    (2019)
(1) magnesium
(2) mercury
(3) zinc
(4) iron
Ans.
(3)
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE
Zn is an amphoteric element.

Q.18. The correct sequence of thermal stability of the following carbonates is:    (2019)
(1) BaCO3 < CaCO3 < SrCO3 < MgCO3
(2) MgCO3 < CaCO3 < SrCO3 < BaCO3
(3) MgCO3 < SrCO3 < CaCO3 < BaCO3
(4) BaCO3 < SrCO3 < CaCO3 < MgCO3
Ans.
(2)
Thermal stability of alkaline earth metal carbonates increases down the group.
∴ MgCO3 < CaCO3 < SrCO3 < BaCO3

Q.19. The INCORRECT statement is:    (2019)
(1) Lithium is the strongest reducing agent among the alkali metals.
(2) Lithium is least reactive with water among the alkali metals.
(3) LiNO3 decomposes on heating to give LiNO2 and O2.
(4) LiCl crystallises from aqueous solution as LiCl.2H2O.
Ans.
(3)
Lithium nitrate decomposes into its oxide on heating.
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE

Q.20. Among the following, the energy of 2s orbital is lowest in:    (2019)
(1) K
(2) H
(3) Li
(4) Na
Ans.
(1)
As the value of Z (atomic number) increases, energy of orbitals decreases (becomes more -ve value)
∴ Order of energy of 2s orbital is H > Li > Na > K.

Q.21. A metal ‘M’ reacts with nitrogen gas to afford ‘M3N’. ‘M3N’ on heating at high temperature gives back ‘M’ and on reaction with water produces a gas ‘B’. Gas ‘B’ reacts with aqueous solution of CuSO4 to form a deep blue compound. ‘M’ and ‘B’ respectively are:    (2017)
(1) Li and NH3
(2) Na and NH3
(3) Ba and N2
(4) Al and N2 
Ans.
(1)
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE

Q.22. Both lithium and magnesium display several similar properties due to the diagonal relationship, however, the one which is incorrect, is    (2017)
(1) Both form basic carbonates 
(2) Both form soluble bicarbonates
(3) Both form nitrides 
(4) Nitrates of both Li and Mg yield NO2 and O2 on heating  
Ans.
(1)
Lithium can form carbonate (Li2CO3). Lithium Carbonate is not basic in nature. On other hands, Mg can form basic carbonate.
5Mg+2 + 6CO32- + 7H2O → 4MgCO3.Mg(OH)2. 5H2O + 2HCO3-

Q.23. Which one of the following is an oxide?    (2017)
(1) SiO2
(2) KO2
(3) BaO2
(4) CsO2
Ans.
(1)
JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE 

Q.24. Which of the following atoms has the highest first ionization energy?    (2016)
(1) Rb
(2) Na
(3) k
(4) Sc
Ans.
D
Alkali metals have the lowest ionization energy in each period on the other hand Sc is a d-block element.
Transition metals have smaller atomic radii and higher nuclear charge leading to high ionisation energy.

Q.25. The correct order of the solubility of alkaline-earth metal sulphates in water is:    (2016)
(1) Mg < Sr < Ca < Ba
(2) Mg > Ca> Sr > Ba
(3) Mg > Sr > Ca > Ba
(4) Mg < Ca < Sr < Ba
Ans.
(2)
Solubility of sulphates of alkaline earth metal decreases down the group. Hence correct order of solubility is
Mg > Ca > Sr > Ba

Q.26. Identify the reaction which does not liberate hydrogen:    (2016)
(1) Allowing a solution of sodium in liquid ammonia to stand.
(2) Reaction of zinc with aqueous alkali.
(3) Reaction of lithium hydride with B2H6.
(4) Electrolysis of acidified water using Pt electrodes.
Ans.
(3)
B2H6 + 2LiH → 2LiBH4

The document JEE Main Previous year questions (2016-20): The s-Block Elements Notes | Study Chemistry for JEE - JEE is a part of the JEE Course Chemistry for JEE.
All you need of JEE at this link: JEE

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