Answer:
1. Answer : (a) Strongly basic
Explanation: Caesium is an alkali metal. As we move down the group, the basic strength of alkali hydroxide increases Li to Cs.
2. Answer : (b) (Na2CO3. 10H2O)
Explanation: The Solvay process or ammonia-soda process is the major industrial process for the production of sodium carbonate (soda ash, Na2CO3). The ammonia-soda process was developed into its modern form by the Belgian chemist Ernest Solvay during the 1860s.
3. Answer : (a) Deep blue solution
Explanation: Alkali metals dissolve in liquid ammonia giving deep blue solutions, which conduct electricity. The blue colour of the solution is due to ammoniated electrons, which absorb energy in the visible region of light.
4. Answer : (a) Acid containing Oxygen
Explanation: An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bond to oxygen that can dissociate to produce the H+ cation and the anion of the acid. e.g., carbonic acid, H2CO3 (OC(OH)2; sulphuric acid, H2SO4 (O2S(OH)2).
5. Answer : (c) Calcined gypsum
Explanation: The composition of gypsum is CaSO4 ∙2H2O. It does not have CaCO3.
6. Answer : (c) Mg
Explanation: Carnallite is a halide mineral a hydrated potassium magnesium chloride. It is variably colored yellow to white, reddish or blue. It takes place with a series of potassium and magnesium evaporite. Many minerals are composed of calcium.
7. Answer : (a) Mg
Explanation: Austrian Paul Vierkotter used magnesium coated wire in an evacuated glass globe to create the first modern photoflash bulb (or flashbulb).
8. Answer : (d) KOH
Explanation: Potassium hydroxide or caustic potash (KOH) is the strongest base among these hydroxides. Basic strength of hydroxide increase in a group from top to bottom and decrease in a period from left to right.
9. Answer : (d) Cs
Explanation: Cesium (Cs), because as the size of the metal increases, the strength of metallic bonding decreases and hence its meling point decreases. Since the size of Cs is the biggest, therefore its melting point is the lowest.
10. Answer : (b) Na+
Explanation: Hydration energy depends on charge of ion and ionic radius. Higher the charge, greater the hydration energy. On the other hand, smaller the size, greater the hydration energy. Charge is considered first for comparison. Hence, Mg2+ has higher hydration energy than Na+.
11. Answer : (c) Ca3(PO4)2
Explanation: Both Ca and P are needed by human beings. Also they prevent moisture absorbing power of other components such as MgCl2, CaCl2, CaSO4 and MgSO4 present in commercial sodium chloride.
12. Answer : (d) Fe
Explanation: Method of extraction of a metal depends on the reactivity of the metal. Iron (Fe) is not manufacture by electrolysis. Moderately reactive metals like zinc and iron are extracted by reduction of their oxides using carbon.
13. Answer : (a) H2
Explanation: In such cases, electrolysis of brine gives hydrogen gas at the cathode and chlorine gas at the anode.
14. Answer : (a) Francium
Explanation: Naturally occurring radioactive metals include polonium (Po), francium (Fr), radium (Ra), actinium (Ac), thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), and plutonium (Pu).
15. Answer : (a) Ionic radius
Explanation: The ionic radii of alkali metal increases as the atomic number increases when we move form top to bottom because on moving down the group .There is a increase in the number of shells and therefore, ionic radii increases.
16. Answer : (a) Rb
Explanation: The reason for flame colouration is that the energy of the flame causes an excitation of the outermost electrons which when return to their original position, give out the energy so absorbed in the visible region. Thus, Rb gives a red-violet colour to the flame.
17. Answer : (a) Li
Explanation: Lithium (Li) is the alkali metal which forms only normal oxide, Li2O when heated in air.
2Li +1/2O2 → Li2O
18. Answer : (a) KO2
Explanation: KO2 is used because it not only provides oxygen but also removes CO2 both of which are important life supporting processes.
19. Answer : (a) LiF
Explanation: The electronegativity of halogens is as F > Cl > Br > I . Among alkali metals the electropositive character increases as Li < Na < K < Rb < ds. Hence, LiF is the most stable compound.
20. Answer : (a) NaF
Explanation: Sodium fluoride (NaF) shows highest lattice energy among these compounds since Na+ features ions of the same charge, the lattice energy increases as the size of the ions increases.
21. Answer : (c) crystal absorbs moisture and CO2
Explanation: Sodium hydroxide is hygroscopic. When exposed to air, it absorbs moisture and carbon dioxide and forms sodium carbonate.
22. Answer : (c) conc. solution of NaCl
Explanation: Brine is a high-concentration solution of salt (NaCl) in water (H2O).Brine forms naturally due to evaporation of ground saline water but it is also generated in the mining of sodium chloride.
23. Answer : (c) LiNO3
Explanation: Alkali metal nitrates, except lithium, decompose upon strong heating to give oxygen gas and a metal nitrite.
24. Answer : (a) Good conductors of heat and electricity
Explanation: These elements are also excellent conductors of heat and electricity. The alkali metals are very reactive and so are usually found in compounds with other elements, such as salt (sodium chloride, NaCl) and potassium chloride (KCl).
25. Answer : (a) Li
Explanation: Alkali metals that react with nitrogen directly to form nitride is Li. This anamolous behaviour is due to its small size and high polarizing power.
6Li + N2(g) → 2Li3N
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