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s - Block Elements

 (Alkali and Alkaline Earth Metals)

 Group - I Elements: Alkali Metals

1. Incorrect statement among the following is
     1) Lithium salts are mostly hydrated
     2) Lithium reacts with water less vigorously than sodium.
     3) Among alkali metal carbonates, Li2CO3 is thermally unstable.
     4) all the alkali metal hydrogen carbonates are solids.
Ans: (4)
Explanation: LiHCO3 is liquid, other bicarbonates of the group I are solids.

 

2. Potassium carbonate can not be prepared by Solvay process, because
     1) It is lengthy process
     2) KHCO3 is more soluble in water, so it cannot be isolated
     3) K2CO3 obtained is highly impure
     4) all the above
Ans: (2)
Explanation: K2CO3 can not be manufactured as KHCO3 is more soluble in water so it can not be isolated.

 

3. The compound(s) formed when Na2CO3 is dissolved in water is/ are
     1) NaOH only                2) NaHCO3 & NaOH
     3) Na2O & H2CO3        4) Na2O2, NaOH
Ans: (2)
Explanation: Na2CO3 + H2O  NaHCO3 + NaOH

4. When an alkali metal dissolves in liquid ammonia the solution is
     1) blue coloured            2) paramagnetic
     3) mixed conductor      4) all the above
Ans: (4)
Explanation: All are correct, due to presence of ammoniated e-.
       M + (X + Y)NH3  [M(NH3)X]+ + [e(NH3)Y]-

 

5. If S is sublimation energy, I.E. is ionization enthalpy and H.E. is hydration enthalpy, the relation for standard electrode potential E° is
     1) E° = S + I.E. + H.E.      2) E° =  S + I.E. + 2 H.E.
     3) E° = S - I.E. + H.E.      4) E° = S + I.E. +  H.E.
Ans: (1)
Explanation: E° = S + I.E. + H.E.

 

6. The overall reaction takes place in Solvay process is
     1) 2 NH3 + H2O + CO2  (NH4)2CO3
     2) 2 NaCl + CaCO3  Na2CO3 + CaCl2
     3) NH3 + H2O + CO2  NH4HCO3 
    
     
Ans: (2)
Explanation: overall reaction: 2 NaCl + CaCO3  Na2CO3 + CaCl2

 

7. The compound used in making soft soaps is
     1) NaOH      2) NaCl      3) KOH      4) KCl
Ans: (3)
Explanation: KOH is used in soft soaps.

 

8. The mass of water lost when 1 mole of washing soda is heated upto 375 K and above 375 K are respectively
     1) 180 g, 0 g      2) 90 g, 90 g      3) 18 g, 162 g      4) 162 g, 18 g
Ans: (4)

 

9. The ratio of Na & K present in human body are respectively
     1) 9 : 5      2) 17 : 5      3) 9 : 17      4) 17 : 9
Ans: (3)
Explanation: Weights of Na : K = 90 g : 170 g (in a 70 kg man) 
                                                     = 9 : 17

 

10. Ion(s) responsible for the transmission of nerve signals is/ are
     1) Mg+2 & Ca+2      2) Na+, K+     3) both 1 & 2      4) Na+ only
Ans: (2)
Explanation: Na+ & K+ are responsible for the transmission of nerve signals.

 

11. Deliquescent among the following is/ are
     1) CaCl2      2) MgCl2      3) NaOH      4) all the above
Ans: (4)
Explanation: all absorb moisture (H2O) easily from the atmosphere.

 

12. Solubility of LiF and CsI are low, because
     1) high lattice enthalpy of LiF & low hydration enthalpy of Cs+, I- ions
     2) high lattice enthalpy of LiF & high hydration enthalpy of Cs+, I- ions
     3) low lattice enthalpy of LiF & low hydration enthalpy of Cs+, I- ions
     4) low lattice enthalpy of LiF & high hydration enthalpy of Cs+, I- ions
Ans: (1)
Explanation: LiF has high lattice enthalpy where as hydration enthalpies of Cs+ & I- ions are low. So LiF & CsI are least soluble.

 

13. The following ion is more accumulated in red blood cells of human beings is
        1) Na+       2) K+       3) Ca+2       4) Mg+2
Ans: (2)
Explanation: K+ ions are more accumulated in red blood cells.

 

14. The cabonate that will not decompose on heating is
       1) Li2CO3      2) BaCO3      3) Na2CO3      4) CaCO3
Ans: (3)    
Explanation: Except Li2CO3 all alkali metal carbonates (e.g. : Na2CO3) are highly stable towards heating.

 

15. Super oxides of alkali metals are
     1) Yellow or orange coloured      2) paramagnetic
     3) both 1 & 2                               4) colourless and diamagnetic
Ans: (3)
Explanation: due to presence of odd electron bonding superoxide are yellow or orange coloured and paramagnetic.

 

Group - II Elements: Alkaline Earth Metals

 

16. ‘Be’ shows diagonal relationship with ‘Al’. It is due to
        1) similarity in ionic size               2) similar polarising power
        3) similar electronegativity         4) all the above
Ans: (4)
Explanation: due to all these 3 reasons.

 

17. The reason for adding gypsum to the cement is
       1) to slow down the setting process      2) to fasten the setting process
       3) to strengthen the construction         4) to prevent the cracks
Ans: (1)
Explanation: 2 to 3% gypsum is added to cement to slow down the setting process.

 

18. For a good quality of cement, the ratio of silica to alumina should be between
       1) 1 to 2.5      2) 2.5 to 4      3) 4 to 6.5      4) any ratio
Ans: (2)
Explanation: The ratio of SiO2 to Al2O3 should be between 2.5 to 4.0

 

19. The ratio of iron, magnesium and calcium in an adult body is
       1) 5 : 1 : 24      2) 5 : 1 : 240      3) 1 : 5 : 240      4) 1 : 25 : 120
Ans: (3)
Explanation: an adult body contains 5 g of iron, 25 g of Mg and 1200 g of Ca.

 

20. If the symbols for Dicalcium Silicate is DCS, Tricalcium Silicate is TCS and Tricalcium aluminate is TCA, the correct of their percentages in portland cement is
     1) DCS > TCS > TCA      2) TCA > TCS > DCS
     3) DCS = TCS = TCA      4) TCS > DCS > TCA
Ans: (4)
Explanation: The main ingredients in portland cement are 26% Dicalcium Silicate, 51% Tricalcium Silicate and 11% Tricalcium Aluminate.

 

21. The solubilities of carbonates decrease down the alkaline earth metals due to a decrease in
     1) lattice enthalpies of solids      2) Hydration enthalpies of cations
     3) inter ionic interaction             4) entropy of solution formation
Ans: (2)
Explanation: It is due to decrease in hydration energies of cations.

 

22. Be & Al differ in
 1) exhibiting maximum covalency in compounds
  2) exhibiting amphoteric nature in their oxides
  3) forming covalent hydrides
  4) forming polymeric hydrides
Ans: (1)
Explanation: Maximum covalency exhibited by Be = 4
                      Maximum covalency exhibited by Al = 6.

 

23. The colours given by Ca, Sr and Ba in the flame test are respectively
     1) colourless, crimson, green                2) colourless, apple green, crimson
     3) Brick red, crimson, apple green      4) Brick red, apple green, crimson
Ans: (3)
Explanation: Ca - Brick red, Sr - Crimson, Ba - Apple green.

 

24. The products formed by the reaction between BeO, C, Cl2 at 800 K are
     1) Be2C, Cl2O      2) BeCl2, CO     3) BeCl2, COCl2      4) no reaction
Ans: (2)

 

25. The reaction between Mg & O2, Be & H2O forms respectively
     1) MgO, Be(OH)2      2) MgO, BeO     3) MgO, BeH2      4) no reaction
Ans: (4)
Explanation: Be & Mg are inert towards O2 & H2O due to formation of oxide film on their surface.

 

26. Match the following:

List - I List - II
A) Cu - Be alloy I) windows of X - ray tubes
B) Be metal II) extraction of metals
C) Ca metal III) tooth paste ingredient
D) MgCO3 IV) high strength springs
  V) as antacid

The correct match is
  A     B    C    D              A     B    C     D 
1) IV    I    II   III      2)  III   I     V    II 
3) III  II    I    IV       4)   IV  V    III  II
Ans: (1)
Explanation: Cu - Be alloy - high strength springs
                       Be metal - windows of X - ray tubes
                       Ca metal- extraction of metals from metal oxides
                       MgCO3 - ingredient of tooth paste.

 

27. Which of the following reaction does not give gaseous products?

 

28. Setting of cement is
       1) Exothermic process                      2) Hydration
       3) Slow due to dicalcium silicate      4) all the above
Ans: (4)
Explanation: all are correct.

 

29. The sulphate having higher hydration energy than the lattice energy is
       1) BaSO4        2) MgSO4        3) SrSO4        4) RaSO4
Ans: (2)
Explanation: For MgSO4, hydration energy of Mg+2 > lattice energy of Mg+2.

30. CaCO3 is
       1) a filler in cosmetics                                                      2) mild abrasive in toothpaste
       3) used in the manufacture of high quality paper            4) all the above
Ans: (4)
Explanation: all uses are correct.